What is the authenticity of the narration regarding the monk Bahira's encounter with the Prophet, peace be upon him, whether the one that mentions he was accompanied by his uncle Abu Talib, or the one that mentions he was accompanied by Abu Bakr, may Allah be pleased with him, when he was eighteen years old?

The report in question was narrated by al-Tirmidhi, Ibn Abi Shaybah, al-Hakim, and others. It was authenticated by al-Albani and many Hadith scholars. The report mentions that Abu Talib traveled to Syria, and the Prophet, peace and blessings be upon him, was with him. When they approached the monk Bahira, he descended to meet them, although he had never done so before. He took the Prophet's hand and said, "This is the Master of the Worlds. This is the Messenger of the Lord of the Worlds, whom Allah sends as a mercy to the worlds." The elders of Quraysh asked him about his knowledge, and he said, "When you came over the mountain pass, no stone or tree remained but prostrated itself, and they do not prostrate except to a prophet. And I recognize him by the Seal of Prophethood below the cartilage of his shoulder, like an apple."

Then he prepared food for them, and when it was brought, the Prophet, peace and blessings be upon him, was tending camels, so they sent for him. He approached, and a cloud shaded him. When he drew near, he found that they had already taken shelter under the shade of the tree, so the tree's shade tilted towards him.

Then he implored them not to take him to the Romans, for if they saw him, they would recognize him by his description and kill him. He looked around and saw seven men approaching from Rome. He met them and asked them the reason for their coming. They said, "We have come for this Prophet who will appear this month, and there is no path left but people have been sent to it." The monk said to them, "Do you think that if Allah wills to accomplish a matter, can anyone among people repel it?" They said, "No."

Then they pledged allegiance to him and stayed with him. The monk asked about the guardian of the Prophet, peace and blessings be upon him, and they informed him that it was Abu Talib. He kept urging him until Abu Talib sent him back. Al-Tirmidhi stated that the Hadith is Hasan Gharib (good but strange), and al-Albani said: Sahih (authentic), but the mention of Bilal in it is Munkar (denounced). As for the narration that Abu Bakr was with him, it is mentioned in some books of Sirah (biography) and Tafsir (exegesis), but no scholar has authenticated it.