In that day, [he] who shall be on the housetop, and his goods in the house, let him not come down to take them away. And likewise he who is in the field, let him not turn back for the things [left] behind.

Remember Lot's wife.

That they should not be as their fathers, a perverse and provoking generation; a generation which set not its heart aright, and its spirit was not steadfast with God.

The children of Ephraim, bending and shooting [with] the bow, turned [back] in the day of battle.

But Barnabas desired to take along with them John called Mark.

But Paul considered it fitting not to take along with them the one who withdrew from them in Pamphylia, and who had not gone together with them to the work.

For Demas has forsaken me, having loved this present world, and traveled to Thessalonica--Crescens to Galatia, Titus to Dalmatia.

But the just shall live by faith, and if he withdraws, My soul has no pleasure in him."

But let him ask in faith, doubting nothing, for he that doubts is like a wave of the sea driven and tossed by the wind.

he is a double-minded man, unstable in all his ways.

For if having escaped from the corruptions of the world by the knowledge of the Lord and Savior Jesus Christ, yet by these, having become entangled they are defeated, the latter end has become worse for them than the first.

But it has happened to them [according to] the [saying] of the true proverb: "A dog returns to his own vomit," and, "A sow, having washed, to her wallowing in the mire."