From Sahih Muslim (Hadith 2832):
A'isha (Allah be pleased with her) reported:I still seem to see the glistening of the perfume where the hair parted on Allah's Messenger's (ﷺ) head as he was in the state of Ihram, and Khalaf (one of the narrators) did not say: As he was in the state of Ihram, but said: That was the perfume of Ihram
Reference: Muslim 2832