Chabad.org — English translation + Rashi
Torah Temimah points to Menachos 53a.
E-Daf.com — Menachos 53a
HebrewBooks / Shas PDF
English: “It shall be matzah” — make it so: from here that all menachos are kneaded with lukewarm water and watched so they do not leaven.
Custom of lukewarm dough and guarding — the unleavened requirement is implemented by controlled kneading and supervision.
Minchah dough is worked in tepid water and guarded against rising. From the Torah’s insistence that the offering “shall be matzah,” the Sages derive the universal practice for all menachos: knead with lukewarm water and keep continuous watch so that no leavening occurs.