2 verses have
observe
in Edition Clear Qur'an by Talal Itani / Al-Ahzaab (The Clans)

33:32O wives of the Prophet! You are not like any other women, if you observe piety. So do not speak too softly, lest the sick at heart lusts after you, but speak in an appropriate manner.

33:49O you who believe! When you marry believing women, but then divorce them before you have touched them, there is no waiting period for you to observe in respect to them; but compensate them, and release them in a graceful manner.