First Death:
2 Nephi 9:15 And it shall come to pass that when all men shall have passed from this FIRST DEATH unto life, insomuch as they have become IMMORTAL, they must appear before the judgment-seat of the Holy One of Israel; and then cometh the judgment, and then must they be judged according to the holy judgment of God.
Alma 11:45 Now, behold, I have spoken unto you concerning the DEATH OF THE MORTAL BODY, and also concerning the resurrection of the mortal body. I say unto you that this mortal body is raised to an immortal body, that is from death, even from the FIRST DEATH unto life, that they can die no more; their spirits uniting with their bodies, never to be divided; thus the whole becoming spiritual and immortal, that they can no more see corruption.
Helaman 14
14 And behold, again, another sign I give unto you, yea, a sign of his death.
15 For behold, he surely must die that salvation may come; yea, it behooveth him and becometh expedient that he dieth, to bring to pass the resurrection of the dead, that thereby men may be brought into the presence of the Lord.
16 Yea, behold, this death [Jesus’ death] bringeth to pass the resurrection, and redeemeth all mankind from the FIRST DEATH—that spiritual death; for all mankind, by the fall of Adam being cut off from the presence of the Lord, are considered as dead, both as to things temporal and to things spiritual.
17 But behold, the resurrection of Christ redeemeth mankind, yea, even all mankind, and bringeth them back into the presence of the Lord.
Second Death:
Jacob 3:11 O my brethren, hearken unto my words; arouse the faculties of your souls; shake yourselves that ye may awake from the slumber of death; and loose yourselves from the pains of hell that ye may not become angels to the devil, to be cast into that lake of fire and brimstone WHICH IS THE SECOND DEATH.
Alma 12:16 And now behold, I say unto you then cometh a death, even a SECOND DEATH, WHICH IS A SPIRITUAL DEATH; then is a time that whosoever dieth in his sins, as to a temporal death, shall also die a spiritual death; yea, he shall die as to things pertaining unto righteousness.
Alma 12:32 Therefore God gave unto them commandments, after having made known unto them the plan of redemption, that they should not do evil, THE PENALTY THEREOF BEING A SECOND DEATH, WHICH WAS AN EVERLASTING DEATH AS TO THINGS PERTAINING UNTO RIGHTEOUSNESS; for on such the plan of redemption could have no power, for the works of justice could not be destroyed, according to the supreme goodness of God.
Alma 13:30 And may the Lord grant unto you repentance, that ye may not bring down his wrath upon you, that ye may not be bound down by the CHAINS OF HELL, that ye may not suffer the SECOND DEATH.
Helaman 14
18 Yea, and it bringeth to pass the condition of repentance, that whosoever repenteth the same is not hewn down and cast into the fire; but whosoever repenteth not is hewn down and cast into the fire; and THERE COMETH UPON THEM AGAIN A SPIRITUAL DEATH, yea, a SECOND DEATH, for they are cut off again as to things pertaining to righteousness.
19 Therefore REPENT YE, REPENT YE, lest by knowing these things and not doing them ye shall suffer yourselves to come under condemnation, and ye are brought down unto this SECOND DEATH.
Seeking YHWH 