"Behold, I am the law, and the light. Look unto me, and endure to the end, and ye shall live; for unto him that endureth to the end will I give eternal life. Behold, I have given unto you the commandments; therefore keep my commandments. And this is the law and the prophets, for they truly testified of me."
It is Christ who is "the law." Not a man or men. Nor even those sent by Him. They are relevant only to the extent they point to Him. When they attract notice for themselves, they interfere with His great work. He alone is the "law." He alone is the "light."
He answers the concerns these listeners have about the source they are now to look to for life and salvation. "Look unto me" He proclaims. He, not the law, is their future. They are to seek for and establish a more direct line of communication between themselves and Him.
He is the "law"--meaning that His words (both in the preceding sermon and in the revelations He will grant them) is to govern. Not a prior set of performances and ordinances.
He is the "light"--meaning, understanding will increase as they choose to follow Him. They will understand with increasing clarity as they move closer to Him. He will illuminate their understanding, because some things can only be apprehended when you draw close enough to Him for them to emerge from darkness and confusion.
"Look unto [Him]"--meaning, it is not a rule-book, ordinances or traditions which are to guide them. He will. Personally. By His involvement in their lives, through revelation, and with the comforter or Holy Ghost which He has promised to send.
"Endure to the end"--meaning, both here and in the hereafter. It will be a great while beyond this life before you have reached the "end" He desires you to attain. Therefore, enduring requires you to fight against all that opposes truth for so long as you are allowed to participate in the battle. Not passively, taking in what is wrong and showing tolerance for it, but instead actively standing for truth as long as you exist, here and hereafter.
"Ye shall live"-- meaning, the kind of life which Christ gives. That life is not mortal, though you will begin it as a mortal. That is life eternal, which is to know Him and His Father. It was designed to begin here.
"To him that endureth to the end I will give eternal life"--meaning, such people will come to live as Christ and His Father live. Or, in other words, to know truth and be filled with light. (D&C 93: 28, 36.)
"Keep my commandments"--meaning, listen and respond to what He directs. Take what He offers. Do not decline to go and do as He bids you to do; not what you presume will please Him, but what He has counseled you to do. If you do not know what that is, then you do not read the scriptures and ask. You are deliberately without knowledge of what He would ask of you.
"This is the law and the prophets"--meaning, the culmination of all that has been given by Him is for man to come to know Him. This was the purpose behind all the symbols, all the rites, all the ordinances. It is still the purpose underlying it all. Come to Him. Not to a building and think yourself redeemed because you are part of a select group welcomed there. Come to Him. Not to a man who will promise you heaven itself, but to Him who will open to you the heavens.
"For they truly testify of [Him]"--meaning they have and do testify of Him. Not of themselves. Not of a program. Not of an organization. Not of men. They testify of Him. Continually. Not intermittently, occasionally and without knowledge of Him. They do not borrow light from others, but they testify of the things which they know from Him. They will always do so. This is one of the ways you can detect "wolves" from "sheep" as they come professing religion. The true sheep will testify of Him whom they know. The wolves will ask you to follow men, and they interfere with knowing Him. Though you do all the wolves bid you to do, yet you will grow more distant from Him.
Our Lord is indeed a consuming fire, and is unwilling to share adoration with mere men claiming themselves to be worthy of adoration. (Deut. 4: 24.)