“The secret of the LORD is with them that fear him; and he will shew them his covenant.” (Psalms 25:14 KJV)
Secret? What secret? The ESV and ASV say “friendship”. In what way could the friendship of the Lord be an especially wonderful secret? John 14:15 and 1 John 5:2 draw a straight line that reveals our love for God by our obedience. Clearly this verse may be stating that same principle differently in the sense that if we have obedience, thus a real love, that these are the people that God is able to show his covenant to at a level that is much more real. So at least in one sense only these that really do love are even capable of seeing a secret like this.
But does this necessarily make it a secret? Could not even those who don’t receive him at least see a covenant, even if they want no part of it? What is it about friendship that makes this genuinely a secret? When we think of “friendship”, we tend to think of a good relationship that makes the interaction between people more pleasant than less pleasant. As though, what needs to be done still needs to be done, but I would rather us be friends than not. It is more like friendship is the frosting on the cake rather than the cake itself, and it may as well be sweeter than sour. To God, “friendship” is nearer the center than the edges. The whole purpose for creating a being was not that it could do complex things, conquer or command great worlds, or study very intellectual material. It was to have a creature that could do what the most advanced machine with the highest levels of intelligence could never do. To love (note not desire) another. Friendship is an important door to that end. If we “fear” in the sense of “respect” and “put God higher” the Lord, then we can begin to see what a secret “friendship” is. Then we can see that all things are more than the reward at some end, the absence of a punishment that we actually deserve, or some better state than we think that we have now. “Friendship” allows a whole new level to the relationship.
“Ye are my friends, if ye do whatsoever I command you. Henceforth I call you not servants; for the servant knoweth not what his lord doeth: but I have called you friends; for all things that I have heard of my Father I have made known unto you.” (John 15:14-15 KJV)