Ps 90:4

“When the great David heard and understood this, he [David] said to him "who dwells in the shelter of the most High; He will overshadow you with his shoulders," which is the same as being behind God (for the shoulder is on the back of the body). Concerning himself David says, "My soul clings close to you, your right hand supports me." You see how Psalms agree with the history. For as the one says that the right hand is a help to the person who has joined himself close behind God, so the other says that the hand touches the person who waits in the rock on the divine voice and prays that he might follow behind.”

“"He shall defend you between His shoulders, and you shall hope under His wings" [Psalm 91:4]. He says this, that your protection may not be to you from yourself, that you may not imagine that you can defend yourself; He will defend you, to deliver you from the hunter's snare, and from an harsh word. The expression, "between His shoulders," may be understood both in front and behind: for the shoulders are about the head; but in the words, "you shall hope under His wings," it is clear that the protection of the wings of God expanded places you between His shoulders, so that God's wings on this side and that have you in the midst, where you shall not fear lest any one hurt you: only be thou careful never to leave that spot, where no foe dares approach. If the hen defends her chickens beneath her wings; how much more shall you be safe beneath the wings of God, even against the devil and his angels, the powers who fly about in mid air like hawks, to carry off the weak young one? For the comparison of the hen to the very Wisdom of God is not without ground; for Christ Himself, our Lord and Saviour, speaks of Himself as likened to a hen; "how often would I have gathered your children," etc. [Matthew 23:37] That Jerusalem would not: let us be willing....If you consider other birds, brethren, you will find many that hatch their eggs, and keep their young warm: but none that weakens herself in sympathy with her chickens, as the hen does. We see swallows, sparrows, and storks outside their nests, without being able to decide whether they have young or no: but we know the hen to be a mother by the weakness of her voice, and the loosening of her feathers: she changes altogether from love for her chickens: she weakens herself because they are weak. Thus since we were weak, the Wisdom of God made Itself weak, when the Word was made flesh, and dwelt in us, [John 1:14] that we might hope under His wings.”

“Since Scripture conceals a manifold understanding beneath a single letter, the expositor ought to bring hidden things forth into the light and make manifest what has been drawn forth through another, more open passage of Scripture, as if I were to expound that verse of the Psalm: Take hold of arms and shield, and rise up to help me, and wished to explain what the divine arms are; I would say that they are his truth and good will: and that this is so must be proved through open Scripture. For it is also written elsewhere: With the shield of your good will you have crowned us; and again: His truth shall compass you about with a shield.”

“The soul is disposed to the gift of fortitude through the unconquerable shield of faith. The devil draws man to the concupiscence of the flesh, to the concupiscence of the eyes, and to the pride of life. What is the means of resisting these? Through truth. "His truth shall encompass you with a shield," namely through faith dwelling within, "you shall not fear the terror of the night." And blessed Peter said: "Your adversary as a roaring lion goes about seeking whom he may devour: whom resist, strong in faith." If we loved truth, we would not fear the devil, because it is written: "The eyes of the Lord behold the whole earth and give fortitude to those who believe in him with a perfect heart."”

“The third part of the perfection of the fear of the Lord consists in the perfect firmness of confidence: because the fear of the Lord is a tower of firmness and confidence, because it renders a person secure from every other fear. "His truth shall encompass you with a shield; you shall not fear the terror of the night, nor the arrow that flies by day, nor the pestilence that walks in darkness, nor the assault and the noonday devil." He who does not fear God must fear everywhere; and he who truly fears God has what no one can take from him. But he who fears something other than God has what ought to be taken from him.”

“In this garden, there is much walking about, for if one is not happy to remain in the first, he goes to the second, and likewise with the others. And so man is compassed about with apples. Hence, in the Canticle: "Stay me up with flowers, compass me about with apples." And in the Psalm: "His truth shall compass thee with a shield." And so, as the intellect is ordained toward the affective dispositions, and faith is the way to charity, so also these enlightenments must pass over into the affective dispositions, in order that the intellect pass from the speculative to the practical.”