After explaining what it means to love the one and only God – Father, Son and Holy Ghost – above all else and that with all Your heart, soul and might always and everywhere … Dr. Martin Luther continues to paraphrase the holy prophet Moses´s in Deuteronomy in the 6th chapter about our faith in God and that we should not tempt God. He writes:

As in the preceding passage he taught the fear of the Lord—that in prosperity we should do what is right, lest we be complacent—so in this statement he teaches us to endure adversity properly, to be secure, safe, and sure that we are in the care of God, who does not leave us, but is close at hand in all our needs. This the unbelieving and godless do not do, for they cling to things.

God is, however, tempted in two ways.

The first way is not to use the necessary things that are at hand but to seek others, which are not at hand. So Satan tempted Christ, commanding Him to cast Himself from the pinnacle of the temple, although there were steps by which He could walk down. So he would tempt God who would refuse to use clothing in cold weather but would expect a sign from heaven to keep him from freezing. Just so the Jews despised the signs at hand and sought another one from heaven (Luke 11:16). So he tempts God who snores and does not want to work, taking for granted that he must be sustained by God without work, although God has promised to provide for him through his work, as Prov. 10:4 says: “The hands of the busy prepare wealth, but the slack hand will hunger.” This vulgar celibacy is like that too. God takes care of sin and the infirmity of the flesh by making a woman and joining her to the man, but foolish men leave her aside and presumptuously attempt continence by a heavenly miracle. It was said earlier too that under the surface sign of things at hand God shows His works and wants us to use them but not to trust in them. For while it is true that the busy hand produces riches, nevertheless what Solomon also said is true, that only the blessing of the Lord makes wealthy men, namely, through the busy hand (Prov. 10:22). For if the busy hand were to be hindered by force, the blessing of the Lord would still enrich. So through the sword He alone gives safety. Nevertheless, the safety of a man is empty, and “my sword [he says] will not save” (Ps. 44:6). But God will save through the sword if it is at hand, and without the sword if it is not available. Hence one must use things, but one must not trust in them. Only in God should one trust, whether that which you may use is at hand or lacking.

Secondly, God is tempted when nothing needed is at hand except the bare and lone Word of God. Of this temptation Moses is really speaking here when he adds: “Just as you tempted in Massah,” where they said quarrelsomely (Ex. 17:2, 7): “Is God among us or not?” For here the godless are not content with the Word; and unless God does what He promised at the time, in the place, and in the manner prescribed by themselves, they give up and do not believe. But to prescribe place, time, or manner to God is actually to tempt Him and to feel about, as it were, whether He is there. But this is nothing else than to want to put limits on God and subject Him to our will; in fact, to deprive Him of His divinity. He should be free, not subject to bounds and limitations, and be the one who prescribes place, means, and time to us. Therefore both temptations are against the First Commandment, that which happens because of sheer lust and prying when things are abundant and that which happens when poverty urges a man and weakness of faith gives him advice. Here you see the most spiritual First Commandment explained by Moses in a most spiritual and perfect way. For he has not yet come to images, but he is first concerned with condemning the desires of godlessness, which are at the root of external idolatries and images.

Martin Luther: Lectures on Deuteronomy LW9 Vol.9 Pages 74-75