Why is it important to avoid contention with others? Elder Russell M. Nelson explained that the answer reaches back into premortal life:
“To understand why the Lord has commanded us not to ‘contend one with another,’ we must know the true source of contention. A Book of Mormon prophet revealed this important knowledge even before the birth of Christ. … [See Helaman 16:22.] …
“Contention existed before the earth was formed. When God’s plan for creation and mortal life on the earth was first announced, sons and daughters of God shouted for joy. The plan was dependent on man’s agency, his subsequent fall from the presence of God, and the merciful provision of a Savior to redeem mankind. Scriptures reveal that Lucifer sought vigorously to amend the plan by destroying the agency of man. …
“Satan’s selfish efforts to alter the plan of God resulted in great contention in heaven. …
“This war in heaven was not a war of bloodshed. It was a war of conflicting ideas—the beginning of contention.
“Scriptures repeatedly warn that the father of contention opposes the plan of our Heavenly Father. Satan’s method relies on the infectious canker of contention. Satan’s motive: to gain personal acclaim even over God Himself” (in Conference Report, Apr. 1989, 85–86; or Ensign, May 1989, 68–69).