مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1856
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn "Abbas that the Prophet (ﷺ) was asked about one who shaves his head before offering a sacrifice, and the like, and he kept saying: "No problem, no problem."
Musnad Ahmad 1857Sahih (Darussalam) [ al-Bukhari (84) and Muslim (1307)]