And God hearkened unto Leah, and she conceived, and bare Jacob the fifth son.

Wesley's Notes

30:17 And God hearkened unto Leah - Perhaps the reason of this contest between Jacob's wives for his company, and their giving him their maids to be his wives, was the earnest desire they had to fulfil the promise made to Abraham (and now lately renewed to Jacob) that his seed should be as the stars of heaven for multitude, and that, in one seed of his, the Messiah, all the nations of the earth shall be blessed. Two sons Leah was now blessed with; the flrst she called Issachar, a hire, reckoning herself well repaid for her mandrakes; nay, (which is a strange construction of the providence) rewarded for giving her maid to her husband. The other she called Zebulun, dwelling, owning God's bounty to her, God has endowed me with a good dowry. Jacob had not endowed her when he married her; but she reckons a family of children, a good dowry.

Matthew Henry's Concise Commentary

30:14-24 The desire, good in itself, but often too great and irregular, of being the mother of the promised Seed, with the honour of having many children, and the reproach of being barren, were causes of this unbecoming contest between the sisters. The truth appears to be, that they were influenced by the promises of God to Abraham; whose posterity were promised the richest blessings, and from whom the Messiah was to descend.