Confessional Lutheran churches, including the Lutheran Church–Missouri Synod and the Wisconsin Evangelical Lutheran Synod, practice closed communion and require catechetical instruction for all people before receiving the Eucharist.[21][22][23][24][25] Failing to do so is condemned by these Lutherans as the sin of unionism.[26] This teaching comes[27] from 1 Corinthians 10:16-17 which says, "Is not the cup of thanksgiving for which we give thanks a participation in the blood of Christ? And is not the bread that we break a participation in the body of Christ? Because there is one loaf, we, who are many, are one body, for we all share the one loaf" and Paul's teaching of fellowship in 1 Corinthians 1:10, "I appeal to you, brothers and sisters, in the name of our Lord Jesus Christ, that all of you agree with one another in what you say and that there be no divisions among you, but that you be perfectly united in mind and thought."