Psa 91:1 He who dwells in the shelter of the Most High will rest in the shadow of the Almighty.
Psa 91:2 I will say of the LORD, “He is my refuge and my fortress, my God, in whom I trust.”
Psa 91:3 Surely he will save you from the fowler’s snare and from the deadly pestilence.
Psa 91:4 He will cover you with his feathers, and under his wings you will find refuge; his faithfulness will be your shield and rampart.
Psa 91:5 You will not fear the terror of night, nor the arrow that flies by day,
Psa 91:6 nor the pestilence that stalks in the darkness, nor the plague that destroys at midday.
Psa 91:7 A thousand may fall at your side, ten thousand at your right hand, but it will not come near you.
Psa 91:8 You will only observe with your eyes and see the punishment of the wicked.
Psa 91:9 If you make the Most High your dwelling—even the LORD, who is my refuge—
Psa 91:10 then no harm will befall you, no disaster will come near your tent.
‘It is impossible that any ill should happen to any man who is beloved of the Lord. Ill to him is no ill, but only good in a mysterious form. Losses enrich him, sickness is his medicine, reproach is his honour, death is his gain.’ (Spurgeon)
Psa 91:11 For he will command his angels concerning you to guard you in all your ways;
The psalm as a whole gives an idealised picture of the true Israelite, and as such looks forward to Christ. It is interesting that in Mt 4:6 the Devil is recorded as citing this verse against Jesus. Jesus’ reply was, “You shall not test the Lord your God.” But in what sense can we say that this divine protection applies supremely to Christ? After all, he suffered and died at the hands of wicked men. The answer is, of course, that God’s protection meant that no harm could be inflicted on Jesus that was outside God’s will. Thus, an angel protected him from early death, Mt 2:13,19, and he survived a number of threats on his life during his adult ministry, Lk 4:28-30 Jn 5:18 8:59 10:31,39. In a subordinate sense, David himself was protected from many hazards, and a Whitefield could claim that he was ‘immortal till his work was done.’
His angels – ‘The plural “angels” shows that there is no allusion to a guardian spirit attending the individual believer, but merely to the angels collectively, as ministering spirits, the instrumental agents of God’s providential care over his people.’ (Alexander)
‘The angels are  a numerous guard. ‘The mountain was full of horses of fire round about Elisha.’ 2 Kings 6:17. ‘The horses and chariots of fire’ were the angels of God to defend the prophet Elisha.  A strong guard. One angel, in a night, slew a hundred and fourscore and five thousand. 2 Kings 19:35. If one angel slew so many, what would an army of angels have done?  The angels are a swift guard; they are ready in an instant to help God’s children. They are described with wings to show their swiftness: they fly to our help. ‘At the beginning of thy supplications the commandment came forth, and I am come.’ Dan 9:23. Here was swift motion for the angel, to come from heaven to earth between the beginning and ending of Daniel’s prayer.  The angels are a watchful guard; not like Saul’s guard, asleep when their lord was in danger. 1 Sam 26:12. The angels are a vigilant guard; they watch over God’s children to defend them. ‘The angel of the Lord encampeth round about them that fear him.’ Ps 34:7. There is an invisible guardianship of angels about God’s children.’ (Thomas Watson)
Psa 91:12 they will lift you up in their hands, so that you will not strike your foot against a stone.
Psa 91:13 You will tread upon the lion and the cobra; you will trample the great lion and the serpent.
Psa 91:14 “Because he loves me,” says the LORD, “I will rescue him; I will protect him, for he acknowledges my name.
Psa 91:15 He will call upon me, and I will answer him; I will be with him in trouble, I will deliver him and honour him.
Psa 91:16 With long life will I satisfy him and show him my salvation.”