Luke 9:62 ESV

2 Peter 2:20-22 ESV
For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overcome, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them. What the true proverb says has happened to them: “The dog returns to its own vomit, and the sow, after washing herself, returns to wallow in the mire.”

Hebrews 10:38 ESV
but my righteous one shall live by faith, and if he shrinks back, my soul has no pleasure in him.”

James 1:6-8 ESV
But let him ask in faith, with no doubting, for the one who doubts is like a wave of the sea that is driven and tossed by the wind. For that person must not suppose that he will receive anything from the Lord; he is a double-minded man, unstable in all his ways.

Luke 17:31-32 ESV
On that day, let the one who is on the housetop, with his goods in the house, not come down to take them away, and likewise let the one who is in the field not turn back. Remember Lot's wife.

Philippians 3:13 ESV
Brothers, I do not consider that I have made it my own. But one thing I do: forgetting what lies behind and straining forward to what lies ahead,