When do we use the doctrine of the Church properly?

We use the doctrine of the Church properly

…when we take heed to be and remain members of the Invisible Church by sincere faith in the Redeemer;

        Examine yourselves whether ye be in the faith; prove your own selves. II Corinthians 13:5

        If ye continue in My Word, then are ye My disciples indeed; and ye  shall know the truth, and the truth shall make you free.  John 8:31-32

...when we adhere to the visible church which teaches and practices the Word of God in all its purity;

They continued steadfastly in the Apostles’ doctrine.  Acts 2:42

when we do all in our power to maintain, promote, and extend this visible church by prayer, personal service, and financial support;

They that were scattered abroad went everywhere, preaching the Word. Acts 8:4

Go ye, therefore, and teach all nations, baptizing them in the name of the

Father and of the Son and of the Holy Ghost.   Matthew 28:19

So hath the Lord ordained that they which preach the Gospel should live of the Gospel.  I Corinthians 9:14

…when we avoid in spiritual matters all false churches and all heterodox organizations and individuals as dangers to our souls.

Beware of false prophets, which come to you in sheep’s clothing; but inwardly they are ravening wolves.   Matthew 7:15

Beloved, believe not every spirit, but try the spirits whether they are of God;  because many false prophets are gone out into the world.  I John 4:1

Now, I beseech you, brethren, mark them which cause divisions and offenses contrary to the doctrine which ye have learned; and avoid them. Romans 16:17

Be ye not unequally yoked together with unbelievers.  For what fellowship hath righteousness with unrighteousness? And what communion hath light with darkness? And what concord hath Christ with Belial? Or what part hath he that believeth with an infidel? And what agreement hath the temple of God with idols? For ye are the temple of the living God, as God hath said, I will dwell in them and walk in them; and I will be their God, and they shall be My people. Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you and will be a Father unto you, and ye shall be My sons and daughters, saith the Lord Almighty.  II Corinthians 6:14-18

Can two walk together, except they be agreed?   Amos 3:3

(Adapted from Exposition of Luther’s Small Catechism, St. Louis, CPH, 1943.)