Calvin on the call of Matthew from Matthew 9:4-13. He explains what we should do if we find ourselves not wanting to associate with sinners in the Church.
He whom you detest appears to you to be unworthy of the grace of Christ. Why then was Christ himself made a sacrifice and a curse, but that he might stretch out his hand to accursed sinners? Now, if we feel disgust at being associated by Baptism and the Lord’s Supper with vile men, and regard our connection with them as a sort of stain upon us, we ought immediately to descend into ourselves, and to search without flattery our own evils. Such an examination will make us willingly allow ourselves to be washed in the same fountain with the most impure, and will hinder us from rejecting the righteousness which he offers indiscriminately to all the ungodly, the life which he offers to the dead and the salvation which he offers to the lost.” (Commentary on the Harmony of the Gospels, p. 402-403)