The fear of the Lord is pure, enduring forever. (Ps. 199)
St. John says, Perfect love casteth out fear (I John 4:18). How is it then that the holy Prophet David says, Fear the Lord, all ye His saints (Ps. 33:)? This shows that there are two kinds off fear: the first, initial, the second perfect; one belongs to beginners, the other to perfect saints, who have attained to the measure of perfect love. He who obeys God ‘s will through fear of torment is still a beginner; and he who fulfills the will of God through love for God in order to please Him, is brought by this love into perfect fear; and through this fear, when once he has tasted the delight of being with God, he is afraid to fall away, is afraid to be deprived of it. It is this perfect fear, born of love, which casts out the initial fear.
— St. Abba Dorotheus, Directions on Spiritual Training
Fear of God is two kinds. The first is generated in us by the threat of punishment. it is through such fear that we develop in due order self-control, patience, hope in God and dispassion; and it is from dispassion that love comes. The second kind of fear is linked with love and constantly produces reverence in the soul, so that it does not grow indifferent to God because of the intimate communion of its love.
— St. Maximos the Confessor, First Century on Love