Genesis 38:4 Midrash

וַתַּ֥הַר ע֖וֹד וַתֵּ֣לֶד בֵּ֑ן וַתִּקְרָ֥א אֶת־שְׁמ֖וֹ אוֹנָֽן׃

And she conceived again, and bore a son; and she called his name Onan.

Read midrashic interpretation of Genesis 38:4: and classical rabbinic exegesis.