1 Corinthians 16:9

Paul occasionally used the door as a metaphor for opportunity (cf. 2 Corinthians 2:12; Colossians 4:3). He stayed in Ephesus three years to take advantage of his opportunities there. He did not regard adversaries there as an indication of a closed door or as a sign that God wanted him to move on to more comfortable ministry. He followed his own advice and remained immovable and abounding in the work of the Lord in Ephesus (1 Corinthians 15:58).