Hadith.4728 - Abu Abdullah (as) was asked about the reason for shaving the head of a newborn. Imam (as) replied: "It is to purify the child from the hair of the womb."
Al-Kāfi #149“I once asked abu al-Hassan (a.s.), about the newborn: if shaving his head after seven days from his birth is required. He (the Imam) said,...