Parashas Bo · Shemos 12:2 · TT note 4
Chabad.org — English translation + Rashi
Torah Temimah on Shemos 12:2 points to the classical use of this verse for Nisan as the head of the months (Rosh Hashanah 7a and related).
Sefaria — Exodus 12:2
Sefaria — Torah Temimah on Exodus 12:2
Sefaria — Rosh Hashanah 7a
E-Daf — Rosh Hashanah 7a
English: The Sages taught: On the first of Nisan is the New Year for months, for intercalations, and for the contribution of shekels. From where do we know [that it is the New Year] for months? As it is written: “This month shall be for you the beginning of the months; it is the first for you of the months of the year.”
Scriptural source for Nisan as the head of the months for several calendar and Temple reckonings.
This passuk establishes Nisan as the starting point for counting months (and related legal new-years listed in the beraisa).