Person looks around in Salah

If a person looks around in Salah in such a way where his chest moves away from the direction of the Qiblah, his Salah will break.

However, if a person looks around in Salah by moving his neck without his chest moving away from the Qiblah, his Salah will not break but to do so is disliked. (Maraqi Falah p.119 & p.125)

The Prophet of Allah Sallallahu Alahi Wasalam said Allah (SWA) continues to turn favourably towards a servant while he is engaged in prayer as long as he does not look to the side (by turning his neck), but if he does so, Allah (SWA) turns away from him. (Sunan Abi Dawud p.138 v.1)