Midrash for Bava Batra 253:3

רב שרביא אמר אף אין אמו טמאה לידה דאמר קרא אשה כי תזריע וילדה זכר וטמאה שבעת ימים עד שיהא זכר משעת לידה

[which implies that] he must be<span class="x" onmousemove="('comment',' V. note 7. ');">⁸</span> a <i>male</i> at<span class="x" onmousemove="('comment',' Lit., 'from'. ');">⁹</span> the time of [his] <i>birth</i>.<span class="x" onmousemove="('comment',' Since Scripture states, man-child&nbsp;…' shall be circumcised'. ');">¹⁰</span> R. Sherabya said: Nor is his mother [levitically] unclean [on account] of [his] birth;<span class="x" onmousemove="('comment',' V. Lev. XII, 2 and 5. ');">¹¹</span>

Sifrei Devarim