And his mercy is on them that fear him from generation to generation. - Luke 1:50

Fear does not cause God to have mercy.  Fear of the Lord is the evidence of the hand of mercy upon a person.

When Jonah ran from his duty to preach to Ninevah, he boarded a ship to get away. The ship soon found herself in the worst storm the mariners had ever seen and they were all afraid. We all, hopefully, know the events of the story which follow. They discover it was Jonah’s fault that they were in trouble. They throw him overboard, and God stops the storm. The Bible then records this:

Then the men feared exceedingly, and offered a sacrifice unto the LORD, and made vows. - Jonah 1:16

The men were afraid before. But after an act of mercy, they feared the Lord exceedingly. Their fear was the evidence of God’s mercy, not the cause.

Another proof that fear does not cause God to have mercy on someone is found in James:

Thou believest that there is one God; thou doest well: the devils also believe, and tremble. - James 2:19

Neither fear, nor even belief, caused a single devil to suddenly become a child of God by obligating God to have mercy on him.

The fear the devils have is fear of their destruction. The fear the child of God has is that he sees that God has the right and power to wipe him off the face of the earth but sovereignly chooses not to!

Peter came to the same conclusion after preaching in Cornelius’s house.

Then Peter opened his mouth, and said, Of a truth I perceive that God is no respecter of persons: But in every nation he that feareth him, and worketh righteousness, is accepted with him. - Acts 10:34-35

The evidence of God’s mercy and salvation of a person has nothing to do with what family they are part of or in which country they are born. The two clearest evidences of mercy in a person’s life are the fear of God and the working of righteousness.

Peter does not include belief in his list. That is not to negate the importance of belief for assurance, but people believe lots of different doctrines. Some of God’s children believe is sovereign grace, some do not. Some of God’s children believe in election and predestination, some do not.  Belief is a hard evidence to evaluate because of doctrinal nuances and peculiarities.  However, “fear of God” and “working righteousness” are pretty clear cut and easy to see.