פּירוש אויף דברים 29:22

גפרית ומלח שרפה כל ארצה, “all of its land having become salt and brimstone;” what is the connection between salt and brimstone? Nothing can withstand fire better than salt, and nothing can be destroyed more totally that when it is treated with brimstone. The Torah means to tell you that if the Israelites had remained loyal to their covenant, they could have withstood any attempt at destruction as salt can withstand it; seeing that they had not, they were destroyed utterly as if they had been rubbed out with brimstone. Brimstone destroys even what the fire had not been able to destroy.

brimstone… They will pray to God that all the land be scorched with brimstone and salt, as in the overthrow of the places mentioned. Some commentators say, however, that the subsequent verb “they will say” [: 23] does not introduce a new sentence, but that it is only a repetition of the previous verb “will say” [: 21]. The verb is repeated, following the rules of Hebrew usage, because of the length of the intervening clause. They i.e., the older generation will answer.

'גפרית ומלח....במהפכת סדום אשר הפך ה, the people seeing this know full well that this was not something accidental but that it is a finger of G’d. The comparison is based on Sodom seeing that its destruction had both been predicted to Avraham and confirmed by Lot and his daughters who were survivors of that event.