Summary: Let’s talk about what message the Holy Spirit had for us, today, when he inspired the psalmist.
The theme statement that my Bible gives for this psalm, right there under the title, is ‘security of the one who trusts in the Lord’.
I propose to you this morning, that the entire script of the Bible, whether specifically or by implication, addresses the security of the one who trusts in the Lord.
Throughout the Old Testament, from the moment God made garments for the man and the woman in the garden (Gen 4:21), to Malachi’s closing remarks:
“But for you who fear My name the sun of righteousness will rise with healing in it’s wings; and you will go forth and skip about like calves from the stall. And you will tread down the wicked, for they shall be ashes under the soles of your feet on the day which I am preparing,’ says the Lord of hosts.”
...from beginning to end, we hear God’s promises of security for the believer, and we see examples of the consequences, of both belief and unbelief.
Through the Gospels Jesus is preaching the coming of the Kingdom of God. He is shouting, “The Kingdom of God is at hand. Repent and believe in the gospel!” “If any man is thirsty, let him come to Me and drink!” “If anyone believes in Me, he will never die!” “I am the Bread of Life!” “Come to Me, all who are weary and heavily burdened, and I will give you rest!”
And the letters of Paul and Peter and James and John and Jude center on the way to be right with God and appropriate to one’s self, security through trust in the Lord.
There are some chapters, in various books, that turn the focus knob and sharpen the picture, and zoom in on this message of security in Him, and Psalm 91 (quickview)  is one of those chapters.
What we generally see in the Psalms, is the result of some historical figure, whether it be David, or Solomon, or some unnamed troubadour, waxing poetic about a time of great trial in his life, and how the Lord saved him through it.
Now, since most of us will never know what it is to have a hunter trying to catch our feet in a snare, or have arrows flying at us in the daytime, or be in a battle, seeing thousands fall dead all around us, in order to profit from the truths stated in this Psalm, we have to see past the surface; past the possible historical application, and ask, “What does the eternal Holy Spirit of God want to relate to me through this song He has provided and preserved and drawn me to?”
For the sake of clarity, I’ve broken it down to these points:
Our PROCLAMATION, His PROTECTION, and His PROMISE
The first application we see from Psalm 91 (quickview)  then, is that the Psalm is giving us a description of the justified. The redeemed. Those, purchased back to God. Those declared right with God, through faith in the shed blood of Christ and His resurrection.
Now of course, the name of Jesus is not mentioned in the Psalm; nor is His death or resurrection. But we know from Biblical doctrine that the one who believes in the promise of a Redeemer ~ the one who believes that God is able to raise men even from the dead, and call into being that which does not exist, is the one who is reckoned right with God.