And now Alma began to expound these things unto him, saying: It is given unto many to know the mysteries of God; nevertheless they are laid under a strict command that they shall not impart only according to the portion of his word which he doth grant unto the children of men, according to the heed and diligence which they give unto him.
And therefore, he that will harden his heart, the same receiveth the lesser portion of the word; and he that will not harden his heart, to him is given the greater portion of the word, until it is given unto him to know the mysteries of God until he know them in full.
And they that will harden their hearts, to them is given the lesser portion of the word until they know nothing concerning his mysteries; and then they are taken captive by the devil, and led by his will down to destruction. Now this is what is meant by the chains of hell.
Original Source
Alma 12:9-11
The Book of Mormon
https://www.lds.org/scriptures/bofm/alma/12?lang=eng#9
Accessed 11/9/2016