Who fed thee in the wilderness with manna, which thy fathers knew not, that he might humble thee, and that he might prove thee, to do thee good at thy latter end;

Wesley's Notes

8:16 That he might humble thee - By keeping thee in a constant dependence upon him for every day's food, and convincing thee what an impotent, helpless creature thou art, having nothing whereon to subsist, and being supported wholly by the alms of divine goodness from day to day. The mercies of God, if duly considered, are as powerful a mean to humble us as the greatest afflictions, because they increase our debts to God, and manifest our dependance upon him, and by making God great, they make us little in our own eyes. To do thee good - That is, that after he hath purged and prepared thee by afflictions, thou mayest receive and enjoy his blessings with less disadvantage, whilst by the remembrance of former afflictions. thou art made thankful for them, and more cautious not to abuse them.

Matthew Henry's Concise Commentary

8:10-20 Moses directs to the duty of a prosperous condition. Let them always remember their Benefactor. In everything we must give thanks. Moses arms them against the temptations of a prosperous condition. When men possess large estates, or are engaged in profitable business, they find the temptation to pride, forgetfulness of God, and carnal-mindedness, very strong; and they are anxious and troubled about many things. In this the believing poor have the advantage; they more easily perceive their supplies coming from the Lord in answer to the prayer of faith; and, strange as it may seem, they find less difficulty in simply trusting him for daily bread. They taste a sweetness therein, which is generally unknown to the rich, while they are also freed from many of their temptations. Forget not God's former dealings with thee. Here is the great secret of Divine Providence. Infinite wisdom and goodness are the source of all the changes and trials believers experience. Israel had many bitter trials, but it was to do them good. Pride is natural to the human heart. Would one suppose that such a people, after their slavery at the brick-kilns, should need the thorns of the wilderness to humble them? But such is man! And they were proved that they might be humbled. None of us live a single week without giving proofs of our weakness, folly, and depravity. To broken-hearted souls alone the Saviour is precious indeed. Nothing can render the most suitable outward and inward trials effectual, but the power of the Spirit of God. See here how God's giving and our getting are reconciled, and apply it to spiritual wealth. All God's gifts are in pursuance of his promises. Moses repeats the warning he had often given of the fatal consequences of forsaking God. Those who follow others in sin, will follow them to destruction. If we do as sinners do, we must expect to fare as sinners fare.