Here are 2 Bible verses about volunteers, curated from both the Old and New Testaments of the Holy Bible, King James Version, arranged from most to least relevant.
Isaiah 1:17 KJV
17 Learn to do well; seek judgment, relieve the oppressed, judge the fatherless, plead for the widow.
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Leviticus 19:32 KJV
32 Thou shalt rise up before the hoary head, and honour the face of the old man, and fear thy God: I am the Lord.