Genesis 30:9

When Leah saw that she had left bearing
For a little while, for she afterwards bore again, and observing also what her sister had done; she took Zilpah her maid, and gave her Jacob to wife:
in this she was less excusable than Rachel, since she had four children of her own, and therefore might have been content without desiring others by her maid; nor had she long left off bearing, and therefore had no reason to give up hope of having any more.