TT #28 · Parshas Tazria · Aliyah 1 · Passuk 3
English: On the eighth day the flesh of his foreskin shall be circumcised.
Chabad.org — Chumash, English translation + Rashi for Vayikra 12:3
Torah Temimah cites Shabbos 135a.
E-Daf — Shabbos 135a · Shas.org · Sefaria — vowelized Shabbos 135a
English: The Shabbos permission also excludes an androgynos, a child born during twilight, and a child born already circumcised.
Limitation by textual precision
The special Shabbos permission for circumcision excludes these doubtful or exceptional cases.