whom He foreknew: Before the people of Israel could do anything to earn their place, God chose them to be his people. He did this because of his grace alone.
Elijah: In 1 Kings 19:1–18, King Ahab had killed many of the Lord’s prophets, and his wife Jezebel threatened to kill Elijah as well. Elijah ran into the wilderness and expressed his deep discouragement. God answered him by saying that many faithful people still remained.
Paul saw a similar situation in his own time. Many Jews did not believe, and some were even hostile to the message about Christ. Even so, God was still at work. He was, and is, preserving a remnant, a smaller group of people who believe.