'Free will offering' in the Bible

And whoever remaineth 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 free-will-offering for the house of God that is in Jerusalem.

And afterward offered the continual burnt-offering, both of the new moons, and of all the set feasts of the LORD that were consecrated, and of every one that willingly offered a free-will-offering to the LORD.

And all the silver and gold that thou canst find in all the province of Babylon, with the free-will-offering of the people, and of the priests, offering willingly for the house of their God which is in Jerusalem:

And I said to them, Ye are holy to the LORD; the vessels are holy also; and the silver and the gold are a free-will-offering to the LORD God of your fathers.