Sunan Abi Dawud 4188
سنن أبي داود#4188SahihNarrated Ibn 'Abbas:The people of the Book used to let their hair hand down, and the polytheists used to part their hair. The Messenger of Allah (ﷺ) like to confirm with the People of the Book in the matters about which he had received no command. Hence he Messenger of Allah (ﷺ) let his forelock hang down but afterwards he parted it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Bukhari (5917) Sahih Muslim (2336)
In-book reference: 35:30