Ps 91:5-7 (BSB says:
5 You will not fear the terror of the night, nor the arrow that flies
by day,
6 nor the pestilence that stalks in the darkness, nor the calamity
that destroys at noon.
7 Though a thousand may fall at your side, and ten thousand at your
right hand, no harm will come near you.
The word "harm" above is not in the Hebrew but is implied. The NIV, NASB etc and similar just have "it". The clear reference to the "harm" (BSB) or "pestilence" (CSB) has its antecedent as:
"terror of the night, nor the arrow that flies by day, nor the pestilence that stalks in the darkness, nor the calamity that destroys at noon."
Note that this includes all threats in a pair of hendiadys - "night and day" plus, "darkness and noon(day)". Thus, the Psalm is a promise of protection from all harm and threats.