'Free will offering' in the Bible

And whosoever is left, in any place where he sojourneth, let the men of his place help him with silver, and with gold, and with goods, and with beasts, besides the freewill-offering for the house of God which is in Jerusalem.

and afterward the continual burnt-offering, and the offerings of the new moons, and of all the set feasts of Jehovah that were consecrated, and of every one that willingly offered a freewill-offering unto Jehovah.

and all the silver and gold that thou shalt find in all the province of Babylon, with the freewill-offering of the people, and of the priests, offering willingly for the house of their God which is in Jerusalem;

And I said unto them, Ye are holy unto Jehovah, and the vessels are holy; and the silver and the gold are a freewill-offering unto Jehovah, the God of your fathers.