John Gill Commentary Genesis 29:34

"And she conceived again, and bare a son. And said, Now this time will my husband be joined unto me, because I have borne him three sons. Therefore was his name called Levi." — Genesis 29:34 (ASV)

And she conceived again, and bore a son A third time, as soon as she well could after the former birth: and said, now this time will my husband be joined to me ; in greater affection and stronger ties of love, and cleave unto her: because I have born him three sons ; which she considered as a threefold cord, binding his affections to her, which could not be easily broke; and therefore was his name called Levi ; which signifies "joined"; from him the Levites sprang, and had their name.