Q. In Keddusha deSidra, the Targum Onkelos of “Hashem reigns forever” is “Hashem, His kingdom rules forever.” Why is the verb “rules” masculine when its subject is “kingdom” is feminine?

A. Horav Shlomo Miller Shlit’a explained that when a feminine subject alludes and implies another masculine subject associated with it, the former is often treated as masculine. An example would be “Matzos yeochel es shivas hayamim” (Shemos 13: 7) Matzos shall be eaten during the seven days. Matzos is a feminine subject, while the verb yeochel is masculine. This is due to the fact that the word Matzos is also in fact the masculine “Lechem” and therefore is often preceded and implied by it, so it is treated as masculine. Another example would be “Yom Hashvi’i, Hashabbos Hagodol Vehakodosh Haze” (Retzeh.)
Although Shabbos is a feminine expression, since it implies and alludes to the “Yom” of Shabbos, it is regarded as a masculine subject.
In “Hashem Malchusei Koem” the targum’s translation of “Hashem Yimloch,” (Shemos 15: 18,) the masculine word “Hashem,” that often precedes and is implied by the rerm “Yimloch,” and now is translated as “His Kingdom,” would be addressed as masculine.
The Rov also pointed out that Torah Shlemah (ibid.) quotes a different girsa namely the feminine “Kayama.” R’ Shmuel Gross also pointed a third girsa in chumash… that evades that term altogether.
(See also Kidushin 2b in regards to the word “derech”

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a