Shaving the Head of the New Convert
As soon as a newborn begins its new life, its prior hair should be shaved. Similarly, as soon as a man impinges on his new life as a Muslim, he should shave his prior hair.
The Prophet (ﷺ) commanded new Muslims to do so. Kulayb al Juhanī (رضي الله عنه) reported that he came to the Prophet (ﷺ) and told him that he had embraced Islām. The Prophet (ﷺ) commanded him:
“Shave off the hair of kufr, and get circumcised.”
[Recorded by Abū Dāwūd and Ahmad. Verified to be hasan by al-Albānī (Sahih ul-Jāmi 1251 and Irwa’-ul-Ghalīl 79)]
Note that circumcision is also required in both cases. Note also that shaving the head of new Muslims applies only to men. We have no authentic reports that the Prophet (ﷺ) commanded any woman who embraced Islām to shave her head.