Sforno on Genesis 21:14/ספורנו על בראשית כ״א:י״ד

1שם על שכמה, the hose containing the water; this was in order to show that she was a slave woman. A reminder of the angel at the time having told her that she was to submit to her mistress Sarah (16,9) A righteous person of the caliber of Avraham would certainly not send away a woman and her son without provisions adequate to ensure that she can reach the next location where new provisions can be obtained. [I wonder why Hagar was not given an animal to ride on? Clearly, Avraham was intent that she should be known to be a slave by the fact that she had to travel on foot. Ed.] Our sages in Bereshit Rabbah 53,15 understand the words ויהי אלוקים את הנער in verse 20, to mean that she had both donkeys and camels at her disposal as well as her son’s servants. If we accept that line in the Midrash at face value, the crisis which overtook Hagar and Ishmael was only that they ran out of water due to having lost their way in the desert. As soon as they found a source of water they had all the means to establish themselves economically, even in the midst of the desert. It was natural for Ishmael to settle in the desert as his mother had been told already while she was pregnant that here son would be a פרא אדם, someone preferring to live in the wilderness, not in civilised society.

2ואת הילד, he also gave her the child;

3וישלחה, he first accompanied her some distance out of his loving concern for them. (compare 18,16).