Psalm 91 declares that God protects the ones who “love” him (v. 14). Whatever the dangers might be, whether from people or events in the natural world, God is the Almighty, the All-powerful One (v. 1). He can and will protect those who love him. Because He will protect, the person who loves him can be at “rest” (v. 1) as God’s perfect love casts out “fear” (v. 5).
Behind this Psalm are the covenant blessings of Deuteronomy 28. The one who loves the Lord with all their heart, or whole-heartedly, is the one who acknowledges who God is (see especially Deut. 6:4). They give God his due out of love for him. And, as a consequence, this type of person can rest in the blessings of the covenant—peace and prosperity under God Almighty’s care.
Ironically, this is the Psalm that Satan quoted when he tempted Jesus (vv. 11-12; cf. Matt 4:6; Luke 4:10-11). He wanted Jesus to obey him, Satan, while assuring Jesus that that choice would not affect God’s care for Him. It’s the age-old ploy of Satan that debuted in the Garden of Eden. He tried to convince Eve that God’s warning of judgment was essentially a bluff (see 3:4). He presents God as if he is the powerless wizard behind the curtain who manipulates and controls people through scaring them away from challenging his authority and from realizing their own god-potential. He encourages Eve to take control of her situation and dictate life to God on her terms. This is essentially what Satan suggests to Jesus. He uses the assurance of God’s care for the righteous as a way to tempt Jesus to put God to the test. He implies God can be manipulated. Jesus does not need to come to God on God’s terms; he can set the terms of their relationship. This type of testing perverts God’s promises into a license to be sinful or foolish. “I can manipulate God on my terms. I can use God’s word of commitment and protection to me to flaunt his will without consequences; he has to forgive me; he has to protect me. That’s his job!” This presents a low view of God and reveals a heart of pride devoid of loving worship.
The one who “dwells in the shelter of the Most High” (v. 1), who comes with love and trust to worship and obey God, does not try to manipulate God or abuse their relationship with God. These “acknowledge” God’s “name” (v. 14). They address God and live in relationship to him in a manner that fits his character and power. They would not consider using God, only worshipping him. They would not consider “testing” him because they know him and trust him. He does not need to prove himself. It would be impossible for them to think that they could or would want to manipulate him to do what they want. God is one to be worshipped and obeyed. He is too great in power and too generous in his love to elevate their will against his or to presume upon his love. He can test them for He has the right and they know he does it for their best. To hold tenaciously to the Almighty with deep affection, genuine trust and unwavering loyalty is the only path of safety, the only path that provides rest for their soul and protection from their enemies (within and without). This is the path Christ perfectly followed. And this is the path of “salvation” for all who follow Christ.