Musar para sa Genesis 22:5

Another difficulty is the commentary of our sages quoted by Rashi on 22,5, where Abraham said to the lads accompanying him ואני והנער נלכה עד כה, "I and the lad will go until there." This is interpreted as a severe criticism of G–d by Abraham who queried, "I want to see where is G–d's promise of כה יהיה זרעך, thus (i.e. so numerous) will be your descendants" (Genesis 15,5). At first glance it appears as if Abraham questioned that G–d would fulfil His promise. How do we reconcile this with G–d's reported rebuke to Moses in Exodus 6,2 describing G–d as having appeared to the patriarchs as א-ל שדי, meaning that G–d did not have any need to justify Himself, seeing that the patriarchs accepted all of G–d's commands without the slightest question (compare Shemot Rabbah 6,4). G–d's comment that He is sorry that the likes of the patriarchs no longer exist seems totally out of place in view of Rashi's interpretation of the words עד כה!