Halakhah for Sanhedrin 108:18

אבל הבא על הזכור והביא זכר עליו הבא על הבהמה והביא בהמה עליו בין לר' אבהו בין לאביי לרבי ישמעאל חייב שלש לרבי עקיבא חייב שתים

Our Rabbis taught: In the case of a male child, a young one is not regardedas on a par with an old one; but a young beast is treated as an oldone.<span class="x" onmousemove="('comment',' The reference is to the passive subject of sodomy. As stated supra 54a, guilt is incurred by the active participant even if the former be a minor, i.e., less than thirteen years old. Now, however, it is stated that within this age a distinction is drawn. ');">²³</span>

Sefer HaChinukh