When Leah conceived and gave birth to her forth child she declared, “This time I will be grateful to G-d.” Leah named her son Yehuda and as a result we are told that Rachel then envied her sister.
We can ask an obvious question: why was Rachel only envious of Leah’s forth child, what about her first three children?
Contrary to what one might think, Rachel’s envy was not about her sister’s bearing children. When Leah had her first son and said, “Now my husband will love me”, Rachel did not react. Nor was she affected when the second son, Shimon, was born and Leah declared that G-d had heard her prayers, and nor with the birth of her third son, Levi, when Leah declared, “Now my husband will join me for I have borne him three sons.”
Only when the forth son was born and Leah said, ”This time I will be grateful to G-d” is when Rachel realized that by not having any children she could not achieve the quality of gratitude that her sister had attained.
It was not Leah’s fertility that Rachel was envious of, but rather Leah’s spiritual attainment that was the natural response to the bountiful blessings that she received.
Although envy is usually a very destructive emotion that our sages said, “Envy removes a person from this world” (Ethics of our fathers, 4:21). That is only if it is directed at another’s earthly possessions and successes, but their spiritual achievements can be a source of positive motivation for us to emulate.