G-d could have led them by way of the cities that were round about them. Instead, G-d led them through the wilderness of fiery serpents and scorpions (Deuteronomy 8:15). And each day’s quantity of food would come to them only from heaven in order to try them and to do them good at the end so that they would believe in Him forever. I have already explained the matter of “trial” in the commentary on the verse, And G-d tried Abraham (Genesis 22:1). ["All trials in the Torah are for the good of the one who is being tried"]

If they will walk in [the way of] My teaching. That is, to see if they would engage in study. Since they received their provisions with very little effort they were expected to study continually.

That I may thus test them: Which is to say: now they are complaining, and justice is on their side because they have no bread to eat. Now I want to fill their lack, so that I will see if they will follow My instructions, and not complain anymore, but rather keep My commandments, seeing that I am benevolent to them, or if even so their hearts will not be right with me.