A:The hair of the new born baby should be shaved on the 7th day. A narration mentions that when Sayyidina Hasan (Radhiyallaahu Anhu) was born to Hadhrat Fatima (Radhiyallaahu Anhaa), Rasulullah (Sallallaahu Alayhi wa Sallam) told her to shave the head and distribute the equivalent to the weight of the hair to the value of silver or gold.
The same was done when Sayyidina Husayn (Radhiyallaahu Anhu) was born. (This was on the seventh day). (Al Mu’jamul Kabeer – Tabraani V1 P311)
It is Sunnah on the seventh day, but if delayed for a valid reason for a few days, it is okay.
Moulana Yusuf Laher