Romans 9:14-16
Paul is writing to the church in Rome about God choosing Israel as the people He chose. Starting at verse 10 he mentioned Isaac who married Rebekah and their sons were Jacob and Esau. God loved Jacob but rejected Esau. This is written in our verse 13 and in Malachi 1:2-3. Paul is trying to point out that God is fair. He will show mercy to anyone He chooses.
The quote in verse 15 is actually Exodus 33:19. This event was God showing Moses His glory. (He also introduced His name of Yahweh.)
Please don’t get me wrong- God WANTS to show His mercy to every soul on earth. He wants a personal relationship with us. I think He said this and Paul re-quoted it as a reminder. We humans might see someone that we don’t think deserves God’s mercy. It’s not OUR place to tell God who He can and can’t show mercy & compassion to. We should be grateful that He show us His mercy and grace!