voluntarily
4 occurrences across the corpus
King James Version
Now when the prince shall prepare a voluntary burnt offering or peace offerings voluntarily unto the LORD, one shall then open him the gate that looketh toward the east, and he shall prepare his burnt offering and his peace offerings, as he did on the sabbath day: then he shall go forth; and after his going forth one shall shut the gate.
KJV Apocrypha (Catholic Deuterocanon)
Then came there unto him a company of Assideans who were mighty men of Israel, even all such as were voluntarily devoted unto the law.
Apostolic Fathers
Now one named Quintus, a Phrygian, who was but lately come from Phrygia, when he saw the wild beasts, became afraid. This was the man who forced himself and some others to come forward voluntarily [for trial]. Him the proconsul, after many entreaties, persuaded to swear and to offer sacrifice. Wherefore, brethren, we do not commend those who give themselves up [to suffering], seeing the gospel does not teach so to do.
OT Pseudepigrapha
And if ye suffer loss voluntarily, or involuntarily, be not vexed; for from vexation ariseth wrath with lying.