is it a Sunnah to cut nails on friday or thursday?

It is Mustahabb (commendable and desirable) to pair the finger nails every Friday. Only a Mujahid is exempted from this and it is preferrable that he lenghtens his nails because it can be used as a weapon to attack the enemy. It was aso the blessed habit of Nabi alaihis salaam that he would pair his nails and not let them grow long. It is also noted in the books on Jurisprudence that he who lengthens his nails, his sustenance and income becomes straitened and restricted. (Shaami vol. 6 pg. 405, H.M. Saeed).

Also, one should remember that at the time of wudhu it is necessary for the validity of the wudhu that water reaches below the nails if the nails are longer than normal. Many a times women are busy in their choirs of the kitchen wherein different types of ingredients tend to stick under the nails and if not removed, Wudhu will be invalid if it does reach the bottom of the nails. Therefore it will not be permissible to keep long nails unnecessarily.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai