I know the title is somewhat anachronistic but you get the the point (I hope):
The relation of the fear of God to the keeping the commandments of God is indicated by the ‘Preacher’ when he says, ‘Let us hear the the conclusion of the whole matter: fear God and keep his commandments; for this is the whole duty of man.’ (Ecclesiastes 12:13). The most practical mundane duties derive their inspiration and impetus from the fear of God (cf. II Samuel 23:3; Colossians 3:22). The highest reaches of sanctification are realized in the fear of God (cf. II Corinthians 7:1).
This emphasis which Scripture places upon the fear of God evinces the bond that exists between religion and ethics. The fear of God is essentially a religious concept; it refers to the conception we entertain of God and the attitude of the heart and mind that is ours by reason of that conception. Since biblical ethic is grounded in and is the fruit of the fear of the Lord, we are apprised again that ethics has its source in religion and as our religion is so will be our ethic. This is to say also that what our whom we worship determines behaviour. What then is the fear of God?
…We have therefore the awe and adoration which the majesty of God must elicit from all rational creatures and we also have the complexion which the fact of our sinfulness must impart to that reverence and adoration.
It is this fear of God that Scripture has in view when it reiterates throughout, ‘Thou shalt fear the Lord thy God.’ The controlling sense of the majesty and holiness of God and the profound reverence which this apprehension elicits constitute the essence of the fear of God.*
*John Murray, Principles of Conduct: Aspects of Biblical Ethics (Grand Rapids: Eerdmans, 1957), pp. 231,237