All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
‘Abdullaah ibn Mughaffal reported on the authority of Abu Hurayrah that the Prophet, sallallaahu ‘alayhi wa sallam, forbade combing one's hair except in intervals. [Abu Dawood, Al-Bayhaqi; Al-Albani: authentic]
Abu Hurayrah narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said: "He who has hair should honor it." [Abu Dawood]
Scholars eliminated the seeming contradiction between the two Ahaadeeth saying that the prohibition to comb one's hair except every other day is for those who suffer from an illness on their heads or cannot comb their hair every day due to an illness or severe coldness. This is a prohibition for doing what constitutes harm to oneself (and not for doing what does not constitute harm).
Ibn Al-Qayyim highlighted that a Muslim is obliged to honor his hair and take good care of it and at the same time is forbidden from going to extremes in taking care of one's hair. He should take good care of his hair in moderation, without indulgence in luxury and self-pampering. Instead, he should comb his hair every other day. The statement of Ibn Al-Qayyim is the best interpretation of the two Ahaadeeth.
Allaah Knows best.