Jamieson, Fausset and Brown on Genesis 19:26

26. Lot was accompanied by his wife and two daughters. But whether it was from irresistible curiosity or perturbation of feeling, or that she was about to return to save something, his wife lingered, and while thus disobeying the parting counsel, "to look not back, nor stay in all the plain" [Ge 19:17], the torrent of liquid lava enveloped her so that she became the victim of her supine indolence or sinful rashness.