The Word of Wisdom
President Joseph F. Smith

The reason undoubtedly why the Word of Wisdom was given--as not by "commandment or constraint" was that at the time, at least, if it had been given as a commandment it would have brought every man, addicted to the use of these noxious things, under condemnation; so the Lord was merciful and gave them a chance to overcome, before He brought them under law. Later on, it was announced from this stand, by President Brigham Young, that the Word of Wisdom was a revelation and a command of the Lord.

(President Joseph F. Smith, CR, Oct. 1913, p. 14)

Section 89

Doctrine & Covenants