NOTES for Psa 91
It is not at all surprising that for centuries people repeated this very psalm in times of danger, drawing from it confidence in God's power and help. The Lord's call “do not be afraid,” which runs throughout Scripture, is unfolded here in images, and we are assured once again that He is near, that He is the chief Defender.
But we also remember how Satan tried to tempt Christ with the words of this very psalm. This means that mechanically repeating even the most wonderful words of prayer is not enough; by themselves they may not frighten God's enemy.
But if the words are inseparable from faith, if the Lord comes first for us and we love Him without hypocrisy and remain faithful to Him, then the words that came by inspiration from the depths of the ancient psalmist's heart can become our armor too, protecting us from every temptation.