Narrated Abu Musa Al-Ash'ari:
"Abu Talib departed to Ash-Sham, and the Prophet (ﷺ) left with him, along with some older men from the Quraish. When they came across the monk they stopped there and began setting up their camp, and the monk came out to them. Before that they used to pass by him and he wouldn't come out nor pay attention to them." He said: "They were setting up their camp when the monk was walking amidst them, until he came and took the hand of the Messenger of Allah (ﷺ). Then he said: 'This is the master of the men and jinn, this is the Messenger of the Lord of the worlds. Allah will raise him as a mercy to the men and jinn.' So some of the older people from the Quraish said: 'What do you know?' He said: 'When you people came along from the road, not a rock nor a tree was left, except that it prostrated, and they do not prostrate except for a Prophet. And I can recognize him by the seal of the Prophethood which is below his shoulder blade, like an apple.' Then he went back, and made them some food, and when he brought it to them, he [the Prophet (ﷺ)] was tending to the camels. So he said: 'Send for him.' So he came, and there was a cloud over him that was shading him. When he came close to the people, he found that they had beaten him to the tree's shade. So when he sat down, the shade of the tree leaned towards him. He (the monk) said: 'Look at the shade of the tree leaning towards him.'" He said: "So while he was standing over them, telling them not to take him to Rome with him - because if the Romans were to see him, they would recognize him by his description, and they would kill him - he turned, and there were seven people who had come from Rome. So he faced them and said: 'Why have you come?' They said: 'We came because this Prophet is going to appear during this month, and there isn't a road left except that people have been sent to it, and we have been informed of him, and we have been send to this road of yours.' So he said: 'Is there anyone better than you behind you?' They said: 'We only have news of him from this road of yours.' He said: 'Do you think that if there is a matter which Allah wishes to bring about, there is anyone among the people who can turn it away?' They said: 'No.'" He said: "So they gave him their pledge, and they stayed with him. And he said: 'I ask you by Allah, which of you is his guardian?' They said: 'Abu Talib.' So he kept adjuring him until Abu Talib returned him (back to Makkah) and he sent Abu Bakr and Bilal with him. And the monk gave him provisions of Ka'k (a type of bread) and olive oil."
English reference: Vol. 1, Book 46, Hadith 3620
Arabic reference: Book 49, Hadith 3980