Authentic Supplication Number 89.

The Messenger of Allah ┬ásaid: “Verily I have been forbidden from the recitation of the Qur’an while bowing or prostrating. As for the bowing, magnify Your Lord in it; and as for the prostration, strive in supplication in it, for it’s worthy that you be granted”.

Reported by Muslim, and is #72 in The Authentic of Good Sayings.