Aishah RA says:
"Rasulullah (SAW) liked to begin with the right while combing his hair; while performing ablution (wudhu) and when putting on his shoes. (Also in every other deed, he first began with the right then the left)."
The manner and act of beginning from the right is not confined to the three acts mentioned in the above Hadith. Rasulullah SAW began everything with the right, and that is why every other deed has been added in the translation of the Hadith. The basic rule is - that all those things that reflect dignity and elegance, while putting on these - the right is preferred, and when removing them the left is begun with, as when putting on clothes, shoes etc. When one enters the Masjid, one enters with the right foot and leaves with the left foot first, as this is the place of dignity and greatness. Contrary to this, in those things that do not have elegance in them, for instance when entering the toilet, when entrance is made with the left foot first.
Abdullah Mughaffal RA reports:
"Rasulullah (SAW) prohibited the combing of hair, but allowed it to be does occasionally."
Qadhi Iyaz RA says that occasionally means after every three days. In the collection of Abu Daud RA a Hadith has been reported, wherein Rasulullah (SAW) prohibited the combing of hair daily. To further explain this, the Ulama have written that it is prohibited at such times when there is no necessity for it, otherwise there is no harm in it. Prohibition is directed to that person whose hair has no dirt in it and does not need grooming. When the hair is dirty, there is no prohibition in combing the hair daily.
Humayd bin Abdurrahman RA relates from a Sahabi that Rasulullah SAW combed his hair occasionally.