Apostles are especial witnesses of Christ. Missionaries represent the Lord, Jesus Christ. Yet, all those who have been baptized take upon themselves His holy name and have covenanted to stand as witnesses of God at all times. That means that one’s demeanor and behavior must be Christ-like in all situations, the locker room, the ball game, the work environment, etc. The scripture condemns the Sunday-only Mormon.
Brigham Young
“Our religion incorporates every act and word of man. No man should go to merchandising unless he does it in God; no man should go to farming or any other business unless he does it in the Lord. No man of council should sit to judge the people but what should judge in the Lord that he may righteously and impartially discern between right and wrong, truth and error, light and darkness, justice and injustice.” (Discourses of Brigham Young, ed. by John A. Widstoe, p. 9)
Brigham Young
“Many of our boys who [play] in the streets and use profane language, know not what they are doing, but there are old men, members of the High Priests’ Quorum, and of the High Council, who, when they get into a difficulty in the [canyon] and are perplexed, will get angry and swear at, and curse everything around them. I will insure that I can find High Priests who conduct in this manner. But on their way home their feelings become mollified, and they wish to plead with the Lord to forgive them. Could you place yourselves in some of our [canyons], or in some other difficult places, out of sight but within hearing, and hear some of the brethren curse and swear at their cattle and horses, you would not have the least idea that they had ever known anything about ’Mormonism,’ but follow them home and you may find them pleading with the Lord for pardon. There are just such characters in our midst.” (Journal of Discourses, vol. 3, p. 275)
Harold B. Lee
“Today we should ask ourselves the question, in answer to what the Master asked of those in His day, ’What think ye of Christ?’ (Matthew 22:42.) …Do I think of Him as the Redeemer of my soul? Do I think of Him with no doubt in my mind as the one who appeared to the Prophet Joseph Smith? Do I believe that He established this church upon the earth? Do I accept Him as the Savior of this world? Am I true to my covenants [made] in the waters of baptism, which, if I understood, meant that I would stand as a witness of Him at all times, and in all things, and in all places, wherever I would be, even until death? (See Mosiah 18:9.)” (The Teachings of Harold B. Lee, p. 8)
M. Russell Ballard
“When we covenant in the waters of baptism to ’stand as witnesses of God at all times and in all things, and in all places,’…It may not always be easy, convenient, or politically correct to stand for truth and right, but it is always the right thing to do. Always!” (Ensign, Nov. 1997, pp. 37-39 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 225)