Westminster Shorter Catechism
Q107

What doth the conclusion of the Lord’s Prayer teach us?

The conclusion of the Lord’s Prayer, which is, For thine is the kingdom, and the power, and the glory, forever. Amen, teacheth us to take our encouragement in prayer from God only225, and in our prayers to praise him, ascribing kingdom, power, and glory to him226; and, in testimony of our desire, and assurance to be heard, we say, Amen227.