2 Corinthians 1:22

who also sealed us, and gave us the earnest of the Spirit in our hearts. ["Every one when he is perfected shall be as his teacher," said Jesus (Luke 6:40). Paul has this truth in mind, and his meaning is as follows: "As God the teacher is a promise-keeper whose yea is absolute, unchangeable and immutable, so also am I, his pupil, a promise-keeper, a yea-man. I showed my approval of promise-keeping, and likewise taught you the value of such a characteristic, in that I, together with my colleagues, preached Christ as he is--a promise-keeper. For God, no matter how varied his promises, is indeed a promise-keeper, so that he has begotten in us that assurance of faith which causes us to say an expectant amen to all his promises, and to glorify him by living as in anticipation of their fulfillment. Such a God could never indorse a promise-breaker, but God has indorsed me. He has established me, with you, in Christ, and by anointing me he has set me apart to the apostolic office, and has sealed me as his own, and has given me the earnest of the Spirit. If I am thus his apostle and still recognized as his, then am I like him, and raised above suspicion of being a pledge-breaker." The seal was then a sign or symbol indicating ownership (Acts 9:15; Ephesians 1:13; Ephesians 4:30; Revelation 7:3; Revelation 9:4). False apostles might attempt to prove their claims by insufficient evidence, such as letters of recommendation, but Paul was truly certified as such by the unction of the Spirit (Acts 9:17; 1 John 2:20). Earnest money was a partial payment given to bind a contract, or given to a servant to encourage and stimulate his faithfulness. As a servant might exhibit such earnest-money in proof of his employment, so Paul pointed to the power of the Spirit in his life as an evidence that he was in the divine service.]