See how little we consult our own happiness, when we presume to dictate to GOD. Compare Genesis 30:1, with this verse. Benoni, is the son of my sorrow. Benjamin means the son of my right hand. Jacob no doubt by the change of the name, meant to place this child near his heart, as a particular token to the memory of his beloved Rachel.
Related Commentaries of Genesis 35:18
Genesis 35:18
18 And it came to pass, as her soul was in departing, (for she died) that she called his name Benoni:d but his father called him Benjamin.