Halq means the complete shaving of the head by the male pilgrim on the 10th of Zul Hijjah. This is the last thing he does before dissolving or getting out of the state of Ihram. For female pilgrims, the requirements of Halq and Taqseer (shortening one’s hair) are satisfied if they trim their hair by approximately half an inch.
The rationale behind shaving the head is that before leaving the sacred places, the pilgrim should pay farewell for the Sacred House. Because of the solemnity of the Sacred House and its unlimited honor, one should pay it farewell while he is totally clean and completely far from filth and impurity. When a servant intends to pay farewell to his master, he is asked to do this while he is in the best of all forms. So, what about the one who intends to pay farewell to Allah the Almighty!