Abraham tried to save Sedom, first in the merit of fifty righteous people, then forty-five, forty, thirty, twenty, and ten. Forty-five (the only non-10 number) is the numerical value of לוט. Lot was in Sedom, and Abraham was trying to save him.
Abraham tried to save Lot based on two ideas. One idea is that Lot was a person of merit. The second idea is that Lot joined him on his journey to Cana’an. Abraham was partially successful. Where the verse says that HaShem would be lenient if the number were found, this means that Lot did not have that merit, because it was not found. But when the verse says that HaShem would be lenient on account of the number, this means that Lot did have that merit.
The first request for fifty contains both of Lot’s potential merits. Abraham, as a person of merit, received an added ה to his name. If Lot was of similar merit, his numerical value would be fifty. Lot also joined Abraham on his journey of לך לך, and both לך and לך equal fifty. These merits would have saved all of Sedom if they were found (Bereishit 18:16), but Lot was not so worthy. He did not surpass his level, and he did not travel to Cana’an with the perfect balance of go and for yourself. Forty-five continues Lot’s personal merit. Although Lot did not surpass himself, he was still Lot (numerical value forty-five). HaShem answered, if I find forty-five. Lot did not live up to expectation.
Forty represents the numerical value of לוט without the ו (which still reads the same way). Lot without the ו is only 39, but the biblical forty lashes are established at thirty-nine. Lot could be humbled and repent for his sins. HaShem answered that He would do so on account of that number. Bereishit (19:18), “And Lot said to them, please no my lord. (19:19) Behold please, your servant has found grace in your eyes, and your kindness was great which you did with me to save my life, but I cannot escape to the mountain, lest the evil attach itself to me and I die. (19:20) Behold please, this city is near to escape there, and it is small. I shall flee there, for it is small, and I will live. (19:21) And he replied to him, behold, I have granted you consideration even regarding this to not overturn the city about which you have spoken.” Lot humbled himself and saved the city of Tzoar.
Thirty continues the other merit that Lot accompanied Abraham on the journey of לך לך, and twenty continues this thought. ל, thirty, represents לך (go) which stresses the lamed, and ך, twenty, represents לך (for yourself) which stresses the chaf. Although Lot did not have the merit of לך לך, perhaps he had the merit of לך (go), but HaShem answered, if I find thirty. Lot did not have this merit. Twenty means that Lot went for לך (himself). Abraham said that even this should protect him. HaShem answered, I will not destroy on account of the twenty. Lot was saved on this merit without the need to humble himself, but he could not go to Tzoar until he did so.
Ten reflects what could be saved. Besides Lot, his wife, and two daughters at home, Bereishit (19:12) states, “…whom else do you have here, a son-in-law (5), your sons (7), your daughters (9), and all that you have in the city (10) remove from the place.” HaShem said, “I will not destroy on account of the ten.”