In Amos 7:1-3,  God sends ordinary, goat-sheep herder Amos a vision.  And Amos had enough sense to know when God was speaking to him.  Even though Amos was a common every day kind of man, he kept his prayer life up.  He was on speaking terms with God.

Incidentally, I use the King James version because that's where I have written my notes in the border for more than 45 years.  But I have taken the liberty to change the thous, thees, haths, etc. to common English.

Amos 7:1-2 "Thus has the Lord God shown to me; and behold, he formed grasshoppers in the beginning of the shooting up of the latter growth; and, lo, it was the latter growth after the king's mowings.  And it came to pass, that when they had made an end of eating the grass of the land, then I said, O Lord God, forgive, I beseech you: by whom shall Jacob (the tribe) arise? for he is small.  The Lord repented  for this: It shall not be, saith the Lord."

The king got the first growth; the grasshoppers got the second growth.  The people starved.  Now whether this was a warning of what was going to happen, or what had already happened, Amos loved the people and desperately called on God to forgive them, to spare them or they would be wiped out.  They were small (few).  The people were guilty of all the sins described in chapters 1-6, but Amos pleaded for another chance for his people.

And then a remarkable thing happened.  God repented!!  God listened to a simple man like you or me, and God changed His mind.  Think of that!!  You and I have the power to change God's mind.  Simply by a sincere plea.  I can't hardly wrap my mind around that.  Prayer changes things.  Prayer can change the mind of God even when people are guilty.  I suppose you would call that ' mercy'.