While the early Saints lived in Kirtland, Ohio, the Lord told them to build a temple. (Read about what happened after the temple was dedicated in D&C 110.) The Lord also told Joseph Smith to start a school to teach Church leaders about the gospel. Many men at this school smoked or chewed tobacco. Joseph and Emma didn’t like the smoky, messy tobacco. When Joseph asked the Lord what to do about it, he received the revelation we now call the Word of Wisdom. You can read it in D&C 89.