Bible Verses About Offerings: Free-will

besides the Shabbats of ADONAI, your gifts, all your vows and all your voluntary offerings that you give to ADONAI

You are to observe the festival of Shavu'ot [weeks] for ADONAI your God with a voluntary offering, which you are to give in accordance with the degree to which ADONAI your God has prospered you.

but if a vow passes your lips, you must take care to perform it according to what you voluntarily vowed to ADONAI your God, what you promised in words spoken aloud.