Is 'Let go and let God' in the Bible?

No — and it is not a paraphrase of one either.

The phrase belongs to the Higher Life or Keswick movement of the 1870s, which taught that beyond conversion lay a second decisive crisis of total surrender, after which the Christian life would become rest rather than struggle. It reached the church through Hannah Whitall Smith’s The Christian’s Secret of a Happy Life and the Keswick Convention, and it reached the recovery world through Frank Buchman’s Oxford Group, which is the immediate parent of Alcoholics Anonymous. Both branches run back to the same source.

The verses usually pressed into service do not support it once you read a few lines further:

• Exodus 14:13 — “stand still and see the salvation of the LORD” is followed four verses later by God telling Moses to have the people go forward. Israel walks all night. The salvation is God’s; the walking is theirs.
• Psalm 46:10 — “be still” is an order given to raging nations to put their weapons down and acknowledge who rules the earth, not a technique for interior passivity.
• Zechariah 4:6 — “not by might, nor by power, but by my Spirit” is spoken to Zerubbabel in the middle of a building project, and verse 9 says his own hands will finish it.
• Philippians 2:12-13 — Paul refuses the dichotomy entirely: work out your salvation because God is the one working in you.

The deeper problem is not the sourcing but the grammar. “Let go” is a command addressed to you, and everything God does in the sentence waits on your performing it. That is not the removal of human contribution; it is its relocation from effort to the cessation of effort. Our confession denies that you have that capacity either. I cannot by my own reason or strength believe in Jesus Christ my Lord or come to him — the will is not bound at the level of doing and free at the level of yielding.

There is a true instinct underneath the phrase, and it is worth honoring: people say it because they have discovered they are not going to be the hero of their own story. That discovery is correct. The slogan simply gives it the wrong shape by making one more act the condition of grace.