Mishkat al-Masabih 4158
Buraida said:
When a boy was born to one of us in the pre-Islamic period he sacrificed a sheep and smeared his head with its blood; but when Islam came we sacrificed a sheep on the seventh day, shaved his head and smeared it with saffron. 

Abu Dawud transmitted it, and Razin added, “and gave him his name.”
عَن بُريدةَ قَالَ: كُنَّا فِي الْجَاهِلَيَّةِ إِذَا وُلِدَ لِأَحَدِنَا غلامٌ ذَبَحَ شاةٌ ولطَّخَ رأسَه بدمه فَلَمَّا جَاءَ الْإِسْلَامُ كُنَّا نَذْبَحُ الشَّاةَ يَوْمَ السَّابِعِ وَنَحْلِقُ رَأْسَهُ وَنُلَطِّخُهُ بِزَعْفَرَانٍ. رَوَاهُ أَبُو دَاوُد وَزَاد رزين: ونُسمِّيه