Midrash for Chullin 278:17

מה דרך שאין קנו בידך אף כל שאין קנו בידך

To teach you, just as on the way the nest cannot be said to be ready at your hand,<span class="x" onmousemove="('comment',' For the birds are not yet caught and certainly not at one's disposal. ihjhpy');">⁷</span>

Sifrei Devarim