Mosiah 5

King Benjamin taught so powerfully with the Spirit that as he finished speaking to his people, they -

"...all cried with one voice, saying: Yea, we believe all the words which thou hast spoken unto us; and also, we know of their surety and truth, because of the Spirit of the Lord Omnipotent, which has wrought a mighty change in us, or in our hearts, that we have no more disposition to do evil, but to do good continually." (Book of Mormon Mosiah 5:2)

And they said -

"...we do rejoice with such exceedingly great joy.
5 And we are willing to enter into a covenant with our God to do his will, and to be obedient to his commandments in all things that he shall command us, all the remainder of our days..." (Book of Mormon Mosiah 5:4 - 5)

Such a covenant is an integral part of the plan of happiness. King Benjamin understood this as he tells them -

"...Ye have spoken the words that I desired; and the covenant which ye have made is a righteous covenant.
7 And now, because of the covenant which ye have made ye shall be called the children of Christ, his sons, and his daughters; for behold, this day he hath spiritually begotten you; for ye say that your hearts are changed through faith on his name; therefore, ye are born of him and have become his sons and his daughters." (Book of Mormon Mosiah 5:6 - 7)

It was in making this covenant that Jesus Christ became the "spiritual Father" in that they were reborn through the power of the atonement and as such -

"...shall know the name by which he is called; for he shall be called by the name of Christ." (Book of Mormon Mosiah 5:9)

The would forever have His name -

"...never should be blotted out, except it be through transgression; therefore, take heed that ye do not transgress, that the name be not blotted out of your hearts." (Book of Mormon Mosiah 5:11)

Because this could happen, King Benjamin -

"...thought it was expedient, after having finished speaking to the people, that he should take the names of all those who had entered into a covenant with God to keep his commandments." (Book of Mormon Mosiah 6:1)

Why? To be -

"...numbered among the people of the church of Christ...that they might be remembered and nourished by the good word of God, to keep them in the right way, to keep them continually watchful unto prayer, relying alone upon the merits of Christ, who was the author and the finisher of their faith." (Book of Mormon Moroni 6:4)