Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.116A.

It is liked that while shaving the head one should first shave the right half, then the left side, while facing the direction of Qiblah, uttering Allahu Akbar, and offering a two rak’ah prayer at the end of it. Waki’ said, “Abu Hanifah once told me: ‘I was mistaken concerning five rites of Hajj and a cupper taught these to me and corrected me. This happened when I went to a cupper and asked him, “How much will you charge for shaving my head?” The cupper said, “Are you from Iraq?” I said, “Yes.” The cupper said to me, “Sit down, this is a rite of Hajj, and on it no conditions must be placed.” I sat down with my face slightly away from the direction of Qiblah. At this he said, “Turn your face toward the Qiblah.” I turned the left side of my head to him to shave it first whereupon he said, “Turn over the right side of your head (that I may shave it first).” I turned the right side to him and he began shaving while I sat quiet. He again said, “Say takbir” which I did, until when I got up to leave, he said, “Where are you going?” I said, “I am going to my camp.” He said, “Offer a two rak’ah prayer first, then leave.” I asked him, “Where did you learn all this?” He replied, “I have seen ‘Ata bin Abi Rabah doing this.””‘ This was reported by Al-Muhib Al-Tabari.