The fear itself, In fear. But how does this square with the high discourse that went before, of perfect assured hope, of faith, and love, and joy, yea, joy unspeakable and glorious, arising out of these? How have all those excellences fallen, as it were, into a dungeon, when fear is mentioned after them! Doesn’t the Apostle St. John say, that perfect love casts out fear?287 And is it not more clearly opposite to perfect or assured hope, and to faith and joy?
If you understand it correctly, this is such a fear as does not prejudice, but preserves those other graces, and the comfort and joy that arise from them: and they all agree so well with it, that they are naturally helps to each other. It would be superfluous to insist on defining this passion of fear, and the many distinctions of it, either with philosophers or divines. The fear here recommended is, out of question, a holy self-suspicion and fear of offending God, which may not only consist with assured hope of salvation, and with faith, and love, and spiritual joy, but is their inseparable companion; as all divine graces are linked together (as the heathens said of their three graces), and, as they dwell together, they grow or decrease together. The more a Christian believes, and loves, and rejoices in the love of God, certainly the more unwilling he is to displease Him, and if in danger of displeasing Him, the more afraid of it; and, on the other side, this fear being the true principle of a wary and holy conversation, fleeing sin, and the occasions of sin, and temptations to it, and resisting them when they make an assault, is as a watch or guard that keeps out the enemies and disturbers of the soul, and so preserves its inward peace, keeps the assurance of faith and hope unmolested, and the joy that they cause, and the communion and societies of love between the soul and her beloved, uninterrupted; all that are then most in danger when this fear abates and falls to slumbering; for then, some notable sin or other is ready to break in and put all into disorder, and for a time make those graces, and the comfort of them to present feeling, as much to seek as if they were not there at all.
Robert Leighton, Commentary on 1 Peter 1:17