A narration by Aisha Bint Abu Bakr (رضي الله عنها) (Prophet's Wife)
Narrated 'Aisha Bint Abu Bakr (the wife of the Prophet) (رضي الله عنها):
"I never remembered my parents believing in any religion other than the true religion (Islam), and (I don't remember) a single day passing without our being visited by Allah's Messenger in the morning and in the evening. When the Muslims were put to test (troubled by the pagans), Abu Bakr (رضي الله عنه) set out migrating to the land of Abyssinia (Ethiopia), and when he reached Bark-al-Ghimad, Ibn Ad-Daghina, the chief of the tribe of Qara, met him and said,
'O Abu Bakr! Where are you going?'

Abu Bakr (رضي الله عنه) replied: 'My people have turned me out (of my country), so I want to wander on the earth and worship my Lord.'

Ibn Ad-Dhagina said: 'O Abu Bakr! A man like you should not leave his homeland, nor should he be driven out, because you help the destitute, earn their living, and you keep good relations with your kith and kin, help the weak and the poor, entertain guests generously, and help the calamity-stricken persons. Therefore, I am your protector. Go back and worship your Lord in your town.'

"So Abu Bakr returned and Ibn Ad-Daghina accompanied him. In the evening Ibn Ad-Dhagina visited the nobles of Quraish and said to them.

'A man like Abu Bakr should not leave his homeland, nor should he be driven out. Do you (Quraish) drive out a man who helps the destitute, earns their living, keeps good relations with his kith and kin, helps the weak and poor, entertain guests generously and helps the calamity-stricken persons?'

So the people of Quraish could not refuse Ibn Ad-Dhagina's protection, and they said to Ibn Ad-Daghina: 'Let Abu Bakr worship his Lord in his house. He can pray and recite there whatever he likes, but he should not hurt us with it, and should not do it publicly, because we are afraid that he may affect our women and children."

Ibn Ad-Dhagina told Abu Bakr all of that. Abu Bakr stayed in that state, worshipping his Lord in his house. He did not pray publicly, nor did he recite Quran outside his house.

Abu Bakr (رضي الله عنه) builds Mosque
"Then a thought occurred to Abu Bakr (رضي الله عنه) to build a mosque in front of his house, and there he used to pray and recite the Quran. The women and children of the pagans began to gather around him in great number. They used to wonder at him and look at him. Abu Bakr was a man who used to weep too much, and he could not help weeping or reciting the Quran. That situation scared the nobles of the pagans of Quraish, so they sent for Ibn Ad-Daghina. When he came to them, they said:
'We accepted your protection of Abu Bakr on condition that he should worship his Lord in his house, but he has violated the conditions and he has built a mosque in front of his house where he prays and recites the Quran publicly. We are not afraid that he may affect our women and children unfavorably. So, prevent him from that. If he likes to confine the worship of his Lord to his house, he may do so, but if he insists on doing that openly, ask him to release you from your obligation to protect him, for we dislike to break our pact with you, but we deny Abu Bakr the right to announce his act publicly.'

Ibn Ad-Dhagina went to Abu Bakr and said:
'O Abu Bakr! You know well what contract I have made on your behalf; now, you are either to abide by it, or else release me from my obligation of protecting you, because I do not want the Arabs hear that my people have dishonored a contract I have made on behalf of another man.'

Abu Bakr (رضي الله عنه) replied: 'I release you from your pact to protect me and am pleased with the protection from Allah.'

Aisha's (رضي الله عنها) narration's continues:
"At that time the Prophet (ﷺ) was in Mecca, and he said to the Muslims:
'In a dream I have been shown your migration place, a land of date palm trees, between two mountains, the two stony tracts.'

So, some people migrated to Medina, and most of those people who had previously migrated to the land of Ethiopia, returned to Medina. Abu Bakr also prepared to leave for Medina, but Allah's Messenger (ﷺ) said to him:
'Wait for awhile, because I hope that I will be allowed to migrate also.'

Abu Bakr replied: 'Do you indeed expect this? Let my father be sacrificed for you!'

The Prophet said: 'Yes.' So Abu Bakr did not migrate for the sake of Allah's Messenger (ﷺ) in order to accompany him.

He fed two she camels he possessed with the leaves of As-Samur tree that fell on being struck by a stick for four months.

"One day, while we were sitting in Abu Bakr's house at noon, someone said to Abu Bakr:
'This is Allah's Messenger with his head covered coming at a time at which he never used to visit us before.'

Abu Bakr (رضي الله عنه) said:
'May my parents be sacrificed for him. By Allah he has not come at this hour except for a great necessity.'

So Allah's Messenger (ﷺ) came and asked permission to enter, and he was allowed to enter. When he entered, he said to Abu Bakr:
"Tell everyone who is present with you to go away.'

Abu Bakr replied: 'There are none but your family, May my father be sacrificed for you, O Allah's Messenger!'

The Prophet (ﷺ) said: 'I have been given permission to migrate.'

Abu Bakr said: 'Shall I accompany you? May my father be sacrificed for you, O Allah's Messenger!'

Allah's Messenger (ﷺ) said: 'Yes.'

Abu Bakr said, 'O Allah's Messenger! May my father be sacrificed for you, take one of these two she-camels of mine.'

Allah's Messenger replied: 'I will accept it with payment.'

So we prepared the baggage quickly and put some journey food in a leather bag for them. Asma, Abu Bakr's daughter, cut a piece from her waist belt and tied the mouth of the leather bag with it, and for that reason she was named 'Dhat-un-Nitaqain' (the owner of two belts).

"Then Allah's Messenger (ﷺ) and Abu Bakr (رضي الله عنه) reached a cave on the mountain of Thaur and stayed there for three nights. Abdullah Ibn Abi Bakr who was an intelligent and sagacious youth, used to stay with them overnight. He used to leave them before daybreak so that in the morning he would be with Quraish as if he had spent the night in Mecca. He would keep in mind any plot made against them and when it became dark he would go and inform them of it.

'Amir Ibn Fuhaira, the freed slave of Abu Bakr(رضي الله عنه), used to bring the milch sheep (of his master, Abu Bakr) to them a little while after nightfall in order to rest the sheep there. So they always had fresh milk at night, the milk of their sheep, and the milk which they warmed by throwing heated stones in it. 'Amir Ibn Fuhaira would then call the herd away when it was still dark (before daybreak). He did the same in each of those three nights.

Allah's Messenger (ﷺ) and Abu Bakr(رضي الله عنه) had hired a man from the tribe of Bani Ad-Dail from the family of Bani Abd Ibn Adi as an expert guide, and he was in alliance with the family of Al-As Ibn Wail As-Sahmi and he was in the religion of the infidels of Quraish. The Prophet (ﷺ) and Abu Bakr (رضي الله عنه) trusted him and gave him their two she-camels and took his promise to bring their two she-camels to the cave of the mountain of Thaur in the morning after three nights later. And when they set out, Amir Ibn Futhaira and the guide went along with them and the guide led them, along the seashore." (Sahih Al-Bukhari).

The nephew of Suraqa Ibn Ju'sham said that his father informed him that he heard Suraqa Ibn Jusham saying:
"The messengers of the pagans of Quraish came to us declaring that they had assigned for the persons who would kill or arrest Allah's Messenger and Abu Bakr, a reward equal to their bloodmoney. While I was sitting in one of the gatherings of my tribe, Bani Mudlij, a man from them came to us and stood up while we were sitting and said: 'O Suraqa! No, I have just seen some people far away on the seashore, and I think they are Muhammad and his companions.'I, too, realized that it must have been they. But I said: 'No, it is not they, but you have seen so-and-so and so-and-so, whom we saw set out.' I stayed in the gathering for a while and then got up and left for my home, and ordered my slave-girl to get my horse, which was behind a hillock, and keep it ready for me.

"Then I took my spear and left by the back door of my house dragging the lower end of the spear on the ground and keeping it low. Then I reached my horse, mounted it and made it gallop. When I approached them (Muhammad and Abu Bakr), my horse stumbled and I fell down from it. Then I stood up, gold hold of my quiver and took out the divining arrows and drew lots as to whether I should harm them or not, and the lot which I disliked came out. But I remounted my horse and let it gallop, giving no importance to the divining arrows. When I heard the recitation of the Qur'an by Allah's Messenger (ﷺ) who did not look hither and thither while Abu Bakr was doing it often, suddenly the forelegs of my horse sank into the ground up to the knees, and I fell down from it.

Then I rebuked it, and it got up but could hardly take out its forelegs from the ground, and when it stood up straight again, its forelegs caused dust to rise up in the sky like smoke. Then again I drew lots with the divining arrows, and the lot which I disliked came out. So I called upon them to feel secure. They stopped, and I remounted my horse and went to them. When I saw how I had been hampered from harming them, it came to my mind that the cause of Allah's Messenger (ﷺ) (Islam) would become victorious.

So I said to them: 'Your people have assigned a reward equal to bloodmoney for your head.'

Then I told them all the plans the people of Mecca had made concerning them. Then I offered them some journey food and goods, but they refused to take anything and did not ask for anything, but the Prophet said: 'Do not tell others about us.'

Then I requested him to write for me a statement of security and peace. He ordered 'Amir Ibn Fuhaira, who wrote it for me on a parchment, and then Allah's Messenger proceeded on his way." (Sahih Al-Bukhari)

Reference: From "Stories of the Prophets" by Al-Imam ibn Kathir and Sahih Al-Bukhari