Commentaries:
Rachel, whose entire married life had been spent desiring to bear sons for Jacob, gave birth to a second boy. Realizing that she was dying from the birth, she named the baby Ben-Oni meaning "son of my sorrow." However, Jacob changed the name of the boy to Benjamin meaning "son of my right hand." Matthew Henry explains:
But Jacob, because he would not renew the sorrowful remembrance of the mother's death every time he called his son by his name, changed his name, and called him Benjamin, the son of my right hand; that is, "very dear to me, set on my right hand for a blessing, the support of my age, like the staff in my right hand."
Not long thereafter, Jacob thought he had lost a son whom he loved dearly. Bringing Joseph's goat's blood-smeared tunic to him, his sons had caused him to believe that Joseph had been killed by a wild beast. With Joseph gone, Jacob placed all his affections on his youngest son, Benjamin, the son of his right hand. Already, Jacob viewed the young Benjamin as the staff in his right hand.
Staff
Benjamin: Son of the Right Hand