Charles Ellicott Commentary Genesis 30:18

"And Leah said, God hath given me my hire, because I gave my handmaid to my husband: and she called his name Issachar." — Genesis 30:18 (ASV)

Issachar. —Hebrew, there is hire. As is so often the case in Hebrew names, there is a double play on the word: for, first, it alluded to the strange fact that Jacob had been hired from Rachel by the mandrakes; but, secondly, Leah gives it a higher meaning, saying, “for God has given me my hire.” In her eyes, the birth of her fifth son was a Divine reward for the self-sacrifice involved in giving her maid to Jacob, a sacrifice that had been followed by years of her own neglect.

As it is also said that God listened to Leah, we may be sure that she had prayed for God’s blessing upon her reunion with her husband; for Calvin’s objection that prayer would scarcely accompany such reprehensible conduct carries little weight. Leah and Rachel were uneducated and untrained country women, whose sole anxiety was to have offspring. Leah was the most religious and best disciplined of the two; and the shame, properly understood, was that she had been forced in this way to buy her husband’s attentions.