Rasulullah (sallallahu ‘alaihi wasallam) was twelve years old when Abu Taalib decided to travel to Syria with a trade caravan of the Quraish. Considering the difficulties encountered in travelling, Abu Taalib did not intend to take Rasulullah (sallallahu ‘alaihi wasallam) with him. However, at the time of departure, he noticed signs of sadness and grief on the blessed face of Rasulullah (sallallahu ‘alaihi wasallam) due to which he decided to take him with.
En route to Syria, they neared the city of Busra where a Christian monk by the name of Jarjis, popularly known as Baheeraa, lived. He was well acquainted with the signs of the final Prophet that were mentioned in the divine books. The moment this trade caravan halted before Baheeraa’s monastery and his gaze fell on the illuminated personage of Rasulullah (sallallahu ‘alaihi wasallam), he at once recognised him as the Prophet referred to in the previous books. Baheeraa then grasped Rasulullah’s (sallallahu ‘alaihi wasallam) hand in his own.
(Extracted from Seeratul Mustafa 1/88-89)