D&C 88

The Savior told His disciples -

"...I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever..."  (New Testament | John 14:16)

Again in our day, He said to His disciples -

"...I now send upon you another Comforter, even upon you my friends, that it may abide in your hearts, even the Holy Spirit of promise; which other Comforter is the same that I promised unto my disciples, as is recorded in the testimony of John."  (Doctrine and Covenants | Section 88:3)

His friends being -

"...they whom my Father hath given me; ye are my friends..."  (Doctrine and Covenants | Section 84:63)

Obviuosly, these are they that have received their saving ordinances and continue to keep their covenants are they given by the Father. 

We learn that this Comforter is the Holy Spirit of promise or the Holy Ghost.  The Holy Ghost is the Holy Spirit that was promised...thus is the Holy Spirit of Promise.  The Lord then teaches the very purpose of this promised Spirit -

"This Comforter is the promise which I give unto you of eternal life, even the glory of the celestial kingdom..."  (Doctrine and Covenants | Section 88:4)

Thus it is this Comforter that leads us to eternal life.  And as we follow His guidance, receive the saving ordinances, and obey the commandments and covenants, such actions then are -

"...sealed by the Holy Spirit of promise..."  (Doctrine and Covenants | Section 132:7)

Or thus approved by this Comforter.