Or HaChaim on Deuteronomy 32:32/אור החיים על דברים ל״ב:ל״ב

1 כי מגפן סדם גפנם, "for their vine is from the vine of Sodom, etc." The Torah here provides the reason why the Jewish people have been "sold" by G'd. The reason Moses says מגפן, from the vineyard instead of simply גפן, is to remind us that everything that exists in the domain of sanctity has its counterpart in the domain of the סטרא אחרא, the spiritually negative domain. This is what we have been taught by Solomon in Kohelet 7,14: "G'd has made the one as well as the other." Israel has been compared to a vine already in Psalms 80,9: "You plucked up a vine from Egypt." The counterpart is the vine originating in Sodom. This is why Moses speaks of Israel in disgrace as representing a vine from Sodom. ענבמו ענבי רוש, "its grapes are grapes of gall." Seeing that not all Israel's branches are vines from Sodom, Moses describes them as containing such parts, i.e. מגפן instead of the whole vine, i.e. גפן. The reason Moses uses the comparison with Sodom is that just as Sodom's measure of guilt was complete before G'd destroyed it, so Israel would not be destroyed until its measure of guilt is complete.

2ומשדמות עמורה, "and from the fields of Gomorrah." On the branches of a holy tree, the higher the branch the more holy its character. The highest branch, due to its extreme holiness, is described in the masculine gender to reflect that this is the one which provides the input, whereas the lowest is described in the feminine gender to reflect the idea that it is the recipient of that input. Moses described Israel's attachment to an evil root. He called the first one גפן, vine, masculine, to describe the fact that it provides the input, whereas the secondary one is described as שדה, field, which is feminine in Hebrew, reflecting its passive role as the recipient of that input. The intelligent reader will understand how to transfer concepts which are familiar from sanctity to its counterpart when dealing with spiritually negative phenomena.