פירוש על ויקרא 26:39

בעונת אבתם אתם means if the iniquities of their fathers shall be with them, i. e. if they hold fast to (imitate) the doings of their fathers (cf. Sifra, Bechukotai, Chapter 8 2; Sanhedrin 27b).

ימקו from the word נמקו חבורותי, “my wounds stink and fester.” The construction is similar to יסעו and יסעו (yissu and yissa-u)

When they hold onto the deeds of their ancestors. Rashi is answering the question: Why does it say “with them”? He is also answering the question: The Torah says, “Fathers shall not be executed through sons, (and sons shall not be executed through fathers)?” Therefore, he explains, “When they hold...”

ימקו — This is an expression denoting “melting away” and therefore means the same as ימסו, “they shall melt away”. Similar to it are (Zechariah 14:12) “[their eyes] shall melt away (תמקנה) in their holes”; (Psalms 38:6) “My wounds נמקו, melt” (i. e. run with pus).