Parashas Bo · Shemos 12:6 · TT note 3
Torah Temimah on Shemos 12:6, note 3 (on לַחֹדֶשׁ הַזֶּה) — the word “this” excludes Pesach Sheni from the four-day inspection requirement.
Sefaria — Exodus 12:6
Sefaria — Torah Temimah on Exodus 12:6
Sefaria — Pesachim 96a
English: “Of this month” — why “this”? To exclude Pesach Sheni, which is like [a one-day] Egypt-Pesach and does not require four days of inspection.
Miut from הַזֶּה: limits the four-day inspection to the primary Pesach, not Pesach Sheni.
Pesach Sheni does not require the four-day pre-slaughter inspection that applies to the main Pesach.