Psalms 51:17

אֲדֹנָי שְׂפָתַי תִּפְתָּח וּפִי יַגִּיד תְּהִלָּתֶךָ

My Master, open my lips and my mouth will declare Your praise.

This verse is recited before the Amidah at every service and is considered an integral part of the prayer. The Metzudas David explains that we ask G-d to forgive our prayers and grant us the ability to sing His praises. We hope that this will then encourage others to forsake their bad ways and to return to Him.