Genesis 21:18 - Ellicott's Commentary On The Whole Bible

Hold him in thine hand. — Literally, strengthen thine hand in him, hold him firmly. As Jerome remarks, the boy thus going hand in hand with his mother must have been her companion in her journey, and not a burden upon her shoulder. We must add that the words do not refer to what she was to do immediately, but to the future. She was not simply to lead him to the water, but to be his brave and faithful protector, such as we learn that she really became.