Paul often uses the word mystery to describe an event at the end of history that God has already decided. This mystery exists in heaven and God reveals it to his people during the Christian era (see 16:25; 1 Corinthians 2:1, 7; 4:1; 15:51; Ephesians 1:9; 3:3, 4, 9; 6:19; Colossians 1:26, 27; 2:2; 4:3; 1 Timothy 3:9, 16). Here, the mystery is the relationship of Jews and Gentiles in the plan of salvation, which is central to this passage (Romans 11:11–32).