Al-Nawawi said in al-Majmoo’ (7/4): Its isnaad is saheeh giving to the situations of al-Bukhaari and Muslim. It was assigned as saheeh by al-Albaani in Saheeh Ibn Maajah.

The knowledge in this hadeeth is the Prophet (peace be upon him) said alayhinna i.e., they must do, which means that it is compulsory.