John on Pulpit Supply

In the operation of a church, from time to time the elders have to decide who they will throw their support behind and who they will oppose.  Should we do a Sunday school class on that new bestseller book?  Should we invite the evangelist that is visiting the neighboring church to talk to us on Sunday night?  Who should our main speaker for our next Missions Conference be?  Should we let the Mayor deliver a speech to the congregation next Sunday morning?

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John, the Elder, provides us some guidance, both positive and negative in his extremely short and to-the-point 2nd and 3rd epistles...

Dear friend, you are faithful in what you are doing for the brothers, even though they are strangers to you. They have told the church about your love. You will do well to send them on their way in a manner worthy of God. It was for the sake of the Name that they went out, receiving no help from the pagans. We ought therefore to show hospitality to such men so that we may work together for the truth. (3John5-8; NIV)

...and...

Many deceivers, who do not acknowledge Jesus Christ as coming in the flesh, have gone out into the world. Any such person is the deceiver and the antichrist. Watch out that you do not lose what you have worked for, but that you may be rewarded fully. Anyone who runs ahead and does not continue in the teaching of Christ does not have God; whoever continues in the teaching has both the Father and the Son. If anyone comes to you and does not bring this teaching, do not take him into your house or welcome him. Anyone who welcomes him shares in his wicked work. (2John7-11)

You want to be involved in the ministries of people who are teaching an orthodox (i.e. apostolic, canonical, biblical) understanding of Christ (3John8).  But if they are teaching some other theology or some other soteriology, you absolutely must not have anything to do with them, not only because you don't want to be lied to, but also because you don't want to lend them support or credence (2John11).