Ephesians 1:13 Sealed With That Holy Spirit of Promise

Ephesians 1:13 (KJV)  In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, 

The power of the gospel to save is attested because it is the word of truth. When one believes in the truth, one finds salvation. The Apostle Paul articulated the gospel:

1 Corinthians 15:3-5 (KJV)  For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures: And that he was seen of Cephas, then of the twelve: 

1 Corinthians 15:6-8 (KJV)  After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep. After that, he was seen of James; then of all the apostles. And last of all he was seen of me also, as of one born out of due time. 

When one confesses his sins and receives Christ, he is sealed with the Holy Spirit of promise.

Romans 10:8-10 (KJV)  But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach; That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. 

In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise. Amen.