'Voluntary offerings' in the Bible

Furthermore, everyone who wishes to repatriate from any territory where he now resides is to receive assistance from his fellow residents in the form of silver, gold, equipment, and pack animals, in addition to voluntary offerings for the Temple of the God of Jerusalem.

So all of their neighbors equipped the travelers with silver, gold, equipment, pack animals, and valuable goods, in addition to voluntary offerings.

After that, they offered all of the continual burnt offerings and the New Moon sacrifices for all of the designated festivals of the LORD that were being consecrated, along with all the voluntary offerings that were dedicated to the LORD.