David’s prayer when both he and the people gave their gold and silver to build the temple is a great example of an offertory prayer.
Blessed are you, O Lord, the God of Israel our father, forever and ever. Yours, O Lord, is the greatness and the power and the glory and the victory and the majesty, for all that is in the heavens and in the earth is yours. Yours is the kingdom, O Lord, and you are exalted as head above all. Both riches and honor come from you, and you rule over all. In your hand are power and might, and in your hand it is to make great and to give strength to all. And now we thank you, our God, and praise your glorious name.
But who am I, and what is my people, that we should be able thus to offer willingly? For all things come from you, and of your own have we given you. For we are strangers before you and sojourners, as all our fathers were. Our days on the earth are like a shadow, and there is no abiding. O Lord our God, all this abundance that we have provided for building you a house for your holy name comes from your hand and is all your own. I know, my God, that you test the heart and have pleasure in uprightness. In the uprightness of my heart I have freely offered all these things, and now I have seen your people, who are present here, offering freely and joyously to you. O Lord, the God of Abraham, Isaac, and Israel, our fathers, keep forever such purposes and thoughts in the hearts of your people, and direct their hearts toward you.