Our good God is greatest of all and for all:

Again, after the manner of a good lawgiver, Moses impresses and repeats the greatness and goodness of the God who commands. “Behold,” he says, “there are various heavens and various gods; but your God is over them all (almost as Paul says in 1 Cor. 8:5). Nevertheless, from all the nations under all the heavens He has loved and chosen your fathers and their seed.” I note that in Scripture the heavens are distributed, not according to spheres, as the mathematicians are accustomed to do but according to parts of the earth, just as the earth, too, is distributed, as he says elsewhere (Deut. 28:23): “And the heavens over your head shall be brass”; that is, there is to be one heaven for this people and another for that people. But this is the God of all the heavens, that is, over all heavens, ruling in the horizon of all—the God, not of the Jews alone but of all nations. Thus Ps. 115:16:⁴ “The heavens are the Lord’s heavens, but the earth He has given to the sons of men.”

Martin Luther´s Commentary on Deuteronomy 10:14 (LW 9 Pg.111)

He loves the sojourner and takes good care of them:

Look at those delightful promises of God: “Who is not partial”; likewise, “Who takes no bribe”; likewise, “He executes judgment for the fatherless and the widow”; likewise, “He loves the sojourner, giving him food and clothing” (vv. 17–18). With these words God clearly consoles all the wretched, lost, and afflicted in the whole world and draws their hearts to Himself, that they may believe in Him and trust in His goodness, as the one and only God demands. If He does not regard persons, I already have something because of which to glory, to puff up my heart, and to be proud against all the kings, princes, rich and strong men of the world. By them I am despised and deserted as poor, mean, and weak. Yet I am certain that I am regarded, sustained, and cared for by Him who is the God of gods and the Lord of lords (as Moses also teems and is magnificent with words here), the powerful one, fearful above all my despisers. What, therefore, would I lack, if some lord of a few servants despises me, while the Lord of all lords and the God of gods deems me worthy of His care?

So if I am a fool, a despairing and despised sinner, or if I have been judged, condemned, and excommunicated as a sinner, heretic, an accursed one, a blasphemer, a servant of Satan—so what? They are holy, righteous, honored, praised, of high repute among the sons of God, and numbered among the stars—so what? Here is the God of gods, who does not regard persons or care for their gifts. He cares for me, a sinner and fool, just as they presume He cares for them. Heavens, if I could hold to these promises in faith, what could happen that could sadden me? What sin could oppress me, what could cause me to despair? Yes, what height, what depth, what present thing, what creature (Rom. 8:38–39) could either puff us up or humble us? Let the heart cling to these words, and nothing will be lacking when all is lost—and nothing will be overly important even when everything is just fine. Only believe that He who says this does not lie, just as He cannot lie; and you shall have a secure and joyous heart in everything and through everything.

See, this is what it means to interpret the First Commandment. This is the commentary of Moses himself. Thus he teaches the understanding of what it means that there is a God, what it means to have God, what it means to fulfill the First Commandment. Oh, what great fountains just these words have been for the prophets! From this source they have drawn whatever they shout forth about the concern of God for the infirm, the lowly, the poor, the sinners, the widows, the orphans, the judged, the condemned, the afflicted, and the wretched; also whatever they thunder against the wealthy, the tyrannical, the mighty, the critical, the violent, the hard, and the proud about the wrath and vengeance of God. For all these flow from the great ocean of the First Commandment and flow back into it, so that no richer consolation or voice is more plainly heard or ever will be heard, yet none harder or severer, than the voice of the First Commandment: “I am the Lord your God.”

And, to proceed to the rest, widows and orphans suffer many things. Who cares for them then? No one, no one at all. But here they shall see with a sure heart, where it is said for their joy: “God of gods, Lord of lords, the great, powerful, and dreadful God—He executes judgment for the widow and the orphan.” This is the source of Ps. 68:5: “The Father of orphans and the Judge of the widow.” He wants this title of glory to be praised and thus to make it evident that out of pure mercy He admonishes tyrants not to do what would force Him to satisfy this title against them. Yet He genuinely frightens them so that they fear to harm widows and orphans, but rather, after His example, do them good and love them. And this is much more remarkable because, whether widows and orphans believe or not, He still executes judgment for them and judges the tyrants, although the unbelief of widows and orphans does not deserve to experience that in this life or while their unbelief lasts. The promise goes on and is fulfilled against the violent and the cruel, even if no one here believes. But it is fulfilled much more powerfully and quickly if the widows and orphans do believe.

He loves strangers so much that He feeds and clothes them. Heavens, who would now rely on his home or patrimony, even though this is not to be despised either? But if in a certain case he should happen to be a wanderer, let him not lose faith or believe less than if he were cherished in his paternal home; but let him sing with the psalmist (27:10): “My father and my mother have forsaken me, but the Lord has received me.” Wisdom 10:10⁶ says of the patriarch Jacob: “She [wisdom] led the righteous one on the right way when he fled from the wrath of his brother, showed him the kingdom of God, gave him the knowledge of sacred things, enriched him by means of his labors, and completed his labors, etc.” Who will doubt that this is why more people become wealthy, prominent, and famous among strangers than at home and in their parental circles? For God is the Father of all; He loves the stranger to the point of giving him food and clothing.

Therefore, rejoice and boast: He is your praise; He is your God.

This is a Hebrew expression. In this passage “praise” seems to me properly to mean what Paul calls in Greek καύχησις (2 Cor. 7:4) or καύχημα (1 Cor. 5:6), “glorying”; in German it is Ruhm. The meaning, then is: “Because of nothing, neither of yourself nor your works, shall you be puffed up or boast. But in your God shall you boast, in Him be puffed up, in Him be proud, since you know that He it is who does not regard persons.”

“And He did with you all these great things which your eyes have seen”; as if He were saying: “You have learned through experience that He gave you food and clothing when you were a stranger, that He does not regard persons, that He judges for the widow and the orphan, etc. Therefore you have something to puff you up and make you proud against all tyrants, yes, against every evil, namely, your God, who provides you with all good things.”

And so you see that it is the fulfillment of the First Commandment to have God be the praise, the boasting, the bragging, the pride of our heart in the time both of prosperity and of adversity. For this it is to have God in truth.