Ephesians 1:13 (KJV) mentions being sealed by the Holy Spirit of Promise:
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,
I can't find that term anywhere else in the Bible. So what is the Holy Spirit of Promise?
It does appear several times in the Doctrine and Covenants so I welcome answers with an LDS perspective. (For example, the D&C passages are about marriage; how does that relate to the context in Ephesians where one is sealed with the Holy Spirit of Promise after hearing the word of truth?)