In Sahih Muslim there is a saying of the Messenger of Allah (Allah’s blessing and peace be upon him) meaning that,

From the begining of the month of Dhul-Hijjah anyone who intends to sacrifice (on Eid al-Adha) should not cut his hair or trim nails until he has offered his sacrifice.

Commenting on it sayyidi wa sanadiHadhrat Mawlana Mohammad Taqi Usmani (may Allah preserve him) said,

‘Maybe this is to immitate the Pilgrims (hujaj) (who in the state of ihram are forbidden to do these activities) and somehow participate in the blessings of the passionate worship of Hajj.’