It is often said that fear of God has no place in the Christian’s life for, “There is no fear in love, but perfect love casts out fear. For fear has to do with punishment, and he who fears (for himself) is not perfected in love” (1 John 4:18).
But there are many commandments to fear in the New Testament; for example, Romans 11:20, “They [the Jews] were broken off because of their unbelief, but you stand fast only through faith. So do not become proud but fear.” Similarly, Hebrews 3:12 warns against unbelief (although the word “fear” is not used): “Take heed, brothers, lest there be in any of you an evil unbelieving heart leading you to fall away from the living God.” (Other texts admonishing fear: 1 Peter 1:17; 2:17; Philippians 2:12-13; Luke 12:5; Isaiah 66:2; Acts 9:31; 2 Corinthians 5:11; 7:1; etc.)

Fitting the Pieces Together

But we shouldn’t get the idea that the writers of the New Testament are taking sides here, some in favor of fear (Paul, Hebrews) and some against (John). For even though Romans 11:20 admonishes fear, Romans 8:15 says, “For you did not receive the spirit of slavery to fall back into fear, but you have received the spirit of sonship.”
And even though Hebrews 3:12 admonishes fear of an unbelieving heart (which is the same as saying the fear of God who requites unbelief with punishment), Hebrews 4:16 says, “Let us with confidence draw near to the throne of grace that we may receive mercy and find grace to help in time of need.”
Therefore, the problem is not so much a disagreement between the authors of the New Testament books, but rather the problem is how the same author can say on the one hand, “Fear!” and on the other hand, “Have no fear! Be confident.” The solution will, I think, be found in the suggestion that a sober fear of God will motivate us to trust his mercy shown in Christ and this “trembling trust” will then gradually remove the fear that drove us to it as we see more clearly what out Lord has done for us.

How Only Perfect Love Casts Out Fear

I was reading Lewis’ Anthology of George MacDonald and found some helpful comments. He points out that absolutely nothing less than perfect love (both from God toward man and man toward God) should cast out fear. We are prone to want to be rid of fear at any cost, by any means. John says there is and should be only one means—perfect love for God should cast out fear.
We think we will be better Christians when we stop fearing—that may be quite false. We will be better Christians when we love God the more for his perfect love. The perfecting of love necessarily drives out fear, but the driving out of fear does not necessarily mean that love is being perfected. One may wish to be rid of fear in the same way he wants to be rid of a bad conscience and he may use all the same deceptive means to shed this discomfort (e.g., alcohol, drugs, or more commonly, the elimination of all the commands in the Bible to fear God and to love him with your whole heart. See Deuteronomy 10:12).
MacDonald writes (page 67),

Persuade men that fear is a vile thing, that it is an insult to God, that he will none of it—while they are yet in love with their own will and slaves to every movement of passionate impulse and what will the consequence be? That they will insult God as a discarded idol, a superstition, a thing to be cast out and spit upon. After that how much will they learn of him?

Love Superior to Fear

Fear is an imperfect bond to God, but it is a bond which should be replaced only by an infinitely closer bond—the bond of love (page 67). Nothing else should cast out fear.
Should fear, then, play a role up to a certain point and never again in the Christian life? The point after which fear will have no proper place in the Christian’s life is the point at which his love is perfected. But none of us is yet perfected in love; none of us is without moments in which his delight in God fades and the “things which are seen” become deceptively attractive.
In these moments we are in need of a warning from Paul (Romans 11:20) or from Hebrews (3:12) or from Jesus (Luke 12:5). In these moments we ought not to be completely free from fear, because we are not completely controlled by love for God; that is, we are not living completely by faith. But the fear that we are to feel as Christians is itself a work of grace. It is a fear which casts us back into love for God and trust in his mercy, and thus destroys itself. Fear is the proper servant of love for imperfect saints.
The second line of “Amazing Grace” is not merely a once-for-all experience:

‘Twas grace that taught my heart to fear,
And grace my fears relieved;
How precious did that grace appear,
The hour I first believed.

Jonathan Edwards on Love and Fear

On January 7, 1974, I found the following quote in Jonathan Edwards’ Treatise Concerning the Religious Affections (London, 1796), p. 102ff. I think it states just what I am trying to say.

So hath God contrived and constituted things in his dispensations toward his own people that when their love decays and the exercises of it fail or become weak, fear should arise; for then they need it to restrain them from sin and to excite them to care for the good of their souls and so to save them up to watchfulness and diligence in religion: but God hath so ordered that when love rises and is in vigorous exercise, then fear should vanish and be driven away for then they need it not, having a higher and more excellent principle in exercise to restrain them from sin and stir them up from their duty.
There are no other principles which human nature is under the influence of that will ever make men conscientious but one of these two, fear or love: and therefore if one of these should not prevail as the other decayed, God’s people when fallen into dead and carnal frames, when love is asleep would be lamentably exposed indeed. And therefore God has wisely ordained, that these two opposite principles of love and fear should rise and fall like the two opposite scales of a balance; when one rises the other sinks…
Fear is cast out by the Spirit of God, no other way than by the prevailing of love: nor is it ever maintained by his Spirit but when love is asleep…