Why does the Torah write "u've'Roshei Chodsheichem" (your Roshei Chodesh), which it does not do for other Yamim-Tovim?
Seforno: Because of Yisrael's self-imposed custom 1 to treat Rosh Chodesh as a sort of mini-Yom-Tov. 2
Seforno: Like we find in Shmuel 1, 20:19.
Seforno: Perhaps the reason for this is because Yisrael's destiny, which is dependent upon Hashem, is similar to that of the moon, which is dependent upon the sun for its light.
Why does the Torah write "u've'Roshei Chodsheichem" (plural), whereas by Shabbos, it writes 'u've'Yom ha'Shabbas" (singular)?
Oznayim la'Torah: Because, whereas each Shabbos is independent, and not connected to the one before , the twelve months, are all part of the year - which is why they are called 'Chodesh ha'Rishon, Chodesh ha'Sheini and Chodesh ha'Shelishi'.
