'Free will offerings' in the Bible

And thither thou shalt come, and thither ye shall bring your burnt sacrifices and your offerings, your tithes and heave offerings of your hands, your vows and free will offerings and thy first born of your oxen and of your sheep.

In the day of thy power shall thy people offer thee free-will offerings with a holy worship; the dew of thy birth is of the womb of the morning.

The firstlings of all the first fruits, and all free will offerings shall be the priest's. Ye shall give unto the priest also the firstlings of your dough, that God may prosper the residue.

Ye made a thank offering of leaven, ye promised free will offerings, and proclaimed them. Such lust had ye, O ye children of Israel,' sayeth the LORD God.