What Old Testament word is behind the word "corrupt" in 2 Corinthians 2:17?
The Old Testament word behind 'corrupt' in 2 Corinthians 2:17 is the term in Isaiah chapter 1 that depicts wine watered down with water. It carries the idea of adulterating a product, which Paul applies to those who peddle a diluted, insincere version of God's Word rather than speaking with sincerity.
Les directs us to Isaiah chapter 1, saying the word translated 'corrupt' in 2 Corinthians 2:17 is the same word. He explains that Paul did not come with a product likened to wine watered down with water, nor as a huckster hawking wares not worth half of what he charged. All of that is wrapped up in the one word 'corrupt.' Paul says many corrupt or hawk the Word of God as an adulterated product, but he came in complete sincerity, as of God, in the sight of God, speaking in Christ. Les notes Paul was defending his apostleship against false teachers and insisting he brought the absolute truth; he connects this to Jude's description of false teachers.
For we are not as many, which corrupt the word of God: but as of sincerity, but as of God, in the sight of God speak we in Christ.