"...Teach ye diligently and my grace shall attend you, that you may be instructed more perfectly in theory, in principle, in doctrine, in all the law of the gospel, in all things that pertain unto the kingdom of God, that are expedient for you to understand;"

Doctrine and Covenants 88:78  

"The most important knowledge in the world is gospel knowledge.  It is knowledge of God and his laws, of those things that men must do to work out their salvation with fear and trembling before the Lord."

President Joseph F. Smith

What is the Gospel?

What is the gospel then?...So often I hear my brethren saying something that I wish we would not say quite that way -- that the gospel is a way of life.  It is not a way of life -- it is the way to eternal life.  It is the science of salvation.
Harold B. Lee