the breaking of all connections with one's home, for the sake of allah alone. after his companions had left for yathrib, the prophet (pbuh) stayed in mecca, waiting for permission from allah to leave the city. abu bakr and ali stayed with him. there were also some muslims whom quraysh had not allowed to leave. abu bakr kept asking the prophet (pbuh) to allow him to go to yathrib, but the messenger of allah (pbuh) kept saying, 'do not be in a hurry; it might be that allah will give you a travelling companion.' the leaders of quraysh assembled in the house of their ancestor, qusayy, as was customary when they had an important decision to make. they had to find a way of getting rid of the prophet muhammad (pbuh), before he was able to join his friends in yathrib. as they were busy arguing, the devil appeared at the door in the form of a noble and handsome old man. when they saw this elderly gentleman standing there, they asked him who he was. he said he was a shaikh from the mountains who had heard what they meant to do and thought he might be able to help or advise them. they thought he looked like a wise man, so they invited him in.
each leader then started to put forward ideas about what should be done, but none of them could agree about which was best, until abujahl told them his plan. this was that each clan should provide a strong, young warrior, each of whom would be given a sword. all the young warriors would then wait outside the prophet's house and together attack him as he came out. in this way they would be rid of him but as the blame for killing him would fall on all the clans, the prophet's family would not be able to seek revenge.

 
when he heard this, the devil in the disguise of the old man, said, 'that man is right; in my opinion it is the only thing to do!' the leaders of quraysh then left to carry out their plan to murder the prophet (pbuh).
in the name of allah, the beneficent, the merciful
"and when the unbelievers plot against thee, to confine thee, or kill thee, or to drive thee out, they were plotting, but allah was (also) plotting; and allah is the best of plotters". (koran iii.30)
before the night fell, on which muhammad (pbuh) was to be killed, the archangel gabriel came to him and said, 'do not sleep tonight in your own bed.' the prophet (pbuh) understood what was going to happen, so he told 'ali to lie in his bed and wrap himself in the blanket that the prophet (pbuh) normally used, promising that no harm would befall him.with the coming of darkness the young men of quraysh had gathered outside the prophet's house, waiting for him to come out. after he had made sure that 'ali was safe,

the prophet (pbuh) left the house. at that very moment allah took away the sight of the warriors so that they could not see the prophet (pbuh), who took a handful of dust, sprinkled it on their heads and recited these verses:
in the name of allah, the beneficent, the merciful
"ya sin by the wise koran, thou art truly among those sent on the straight path; a revelation of the all-mighty, the all-wise, that thou may warn a people whose fathers were never warned, so they are heedless. the word has already proved true of most of them, yet they do not believe. lo! we have put on their necks collars of iron up to the chin, so that they are made stiff-necked. and we have put before them a barrier; and we have covered them so they do not see". (koran xxxvi.1-9)
the young men waited the whole night and were furious when, in the morning, they saw 'ali instead of the prophet (pbuh) coming out of the house.they realised that their plan had failed completely. in the meantime, the prophet (pbuh) went to abu bakr's house and told him, 'allah has told me that now is the time for us to leave mecca.' 'together?' asked abu bakr. 'together', the prophet (pbuh) replied. abu bakr wept for joy, because now he knew that the travelling companion he had been promised was the prophet (pbuh) himself.
then he said,'o messenger of allah, these are the two camels which i have kept ready for this.' and so, the two of them left for a cave in thawr, a mountain to the south of mecca where they intended to hide.
when they were out of the city the prophet (pbuh) looked back and said, 'of all allah's earth, you are the dearest place to allah and to me and if my people had not driven me out i would never have left you.'
when quraysh found out that the prophet (pbuh) and his companion had gone, they set out after them, searching in every direction. three days later they finally reached the cave where the prophet (pbuh) and abu bakr were hiding, but a strange and wonderful thing had happened.

a spider had woven its web right across the entrance to the cave and a dove was nesting with her mate nearby. as the meccans stood in front of the cave, with only the spider's web separating them from the fugitives, abu bakr began to fear for their safety. he whispered to the prophet (pbuh), they are very close. if one of them turns we will be seen.' but he was comforted by the prophet's reply: "what do you think of two who have with them allah as their third? 'grieve not, for verily allah is with us". (koran ix.40) . after a few moments the search parry decided that no one could have entered the cave recently, or the spider's web would not have been complete and the dove would not have nested there, and so they left without searching inside. three days later the prophet (pbuh) and abu bakr thought it safe to leave the cave. abu bakr's son, 'amir, had arranged for three camels and a guide to help them continue their journey to yathrib. 'amir would ride behind his father. the leaders of quraysh,

meanwhile, returned to mecca and offered a reward of one hundred camels to whoever captured the prophet (pbuh). among those who went in search of him was a famous warrior. he was, in fact, the only one to catch up with him, but whenever he came close, his horse would suddenly sink up to its knees in the sand. when this had happened three times, he understood that the prophet (pbuh) was protected by a power stronger than anything he had known, and so he went back to mecca. on arriving there he warned everyone against continuing the search, relating what had happened to him.

in the name of allah, the beneficent, the merciful
"if you do not help him, still allah has helped him already, when the unbelievers drove him forth, (he second of two, when the two were in the cave, when he said to his companion, "grieve not; surely allah is with us." then allah caused his peace and reassurance to descend upon him, and helped him with hosts you cannot see,

and he made the word of the unbelievers the lowest; while allah's word is the uppermost; allah is all-mighty, all-wise". (koran ix.40)
the prophet's journey from mecca is called the hijrah, or migration. it was really the first step towards the spread of islam throughout the entire world, and muslims begin their calendar from the year of the hijrah.