Reference for Sukkah 24:3

זכרים כשרה פשיטא מהו דתימא ניגזור זכרים אטו נקבות קמ"ל

‘With male arrow-shafts it is valid’; but is not this obvious? I might have said that these should be forbidden on account of female ones, therefore he teaches us [that they are not forbidden].

Jastrow