Luther is commenting here on the fear of Abram in Gen 15.1. Notice Luther’s description of God withdrawing himself and what it is meant to accomplish. First, when God withdraws himself it is because of His grace, not in spite of. After all, grace is “truly immovalbe and unchangeable.” But rather, God will from time to time withdraw himself to humble his people and protect them from grievous sins and at the proper time restore their spirits with a word of comfort. The pastoral applications of this are immense. Here are some questions to help you tease this out for yourself. What role does spiritual depression play in formation? When I feel God’s absence, could there be a good and loving reason behind his absence? How does being humbled by God help us to rely on his promises and love Him more?
It is no small comfort, however, to know that grace has not been taken away but is truly immovable and unchangeable, although the awareness and experience of grace is taken away for a time, and dread and fear rush in, discouraging and troubling the spirit. The man becomes impatient, concludes that he cannot bear the wrath of God, and simply makes a devil out of God.
Christ experienced this trial in the garden (Matt 26.41), where nature was wrestling with the spirit, and the spirit indeed was willing but the flesh was weak, terrified, fearful, and troubled. No one is truly sorrowful unless God forsakes him, just as, conversely, no one can be sorrowful when God is present. Therefore sorrow is an indication that God has departed from us and has forsaken us for a time…
When on the other hand, as is written in the Book of Wisdom (3.7), God shines into our hearts with rays of mercy, then it is impossible for our hearts not to be glad, even though we, like Stephen, are being dragged to torture and death.
Therefore it is profitable to consider these examples, namely, that the saints who are bold in the Holy Spirit are bolder than Satan himself. On the other hand, when they are in the clutches of trial, they tremble so much that they are afraid even of a rustling leaf. We are reminded of our weakness in order that no matter how great the gifts are that we possess, we may not exalt ourselves but may remain humble and fear God. From those who do not do this He turns His face away, and trouble and perplexity follow.
I want to preface these remarks to this chapter, in which we learn about what Ps. 4.3 says: “know that God has dealt marvelously with the godly,” that is, that He keeps those who are His occupied in various ways, lest they become heretics, be presumptuous with regard to their gifts, and be puffed up over against those who do not have these gifts. For those who do this are very close to destruction.
Therefore those who are chosen as teachers of the churches to rule over others should offer special prayers that they be preserved from this affliction as from the greatest and most dangerous evil.
Other sins- such as wrathfulness, impatience, and drunkenness- naturally bring shame because of their foulness. Those who indulge in them know that they have sinned. Consequently, they blush. But vainglory and trust in one’s own wisdom or righteousness is a sin of such a kind that it is not recognized as sin. Instead, men thank God for it, as the Pharisee does in the Gospel (Luke 18.9-14); they rejoice in it as in an extraordinary gift of the Holy Spirit. Therefore it is an utterly incurable devilish evil.
From this God preserves saintly Abraham by subjecting the glorious conqueror to such an affliction that it is necessary to comfort him with a divine word…
Luther, Comentary on Genesis vol. II (LW vol. 3 pg 8-9)