The foundational doctrine to the believers is given in the book of Romans.  In Romans 10:9-10 we are born again - saved - by confessing with our mouth the Lord Jesus Christ and believing in our heart that God raised him from the dead.  As born again ones we are all members of the body of Christ and we are all affected by what happens to one another in this body.

I Corinthians 12:25-27
   That there should be no schism [division] in the body; but that the members should have the same care one for another.
   And whether one member suffer, all the members suffer with it; or one member be honoured, all the members rejoice with it.
   Now ye are the body of Christ, and members in particular.

   In the body of Christ we are to have the same care one for another.  What happens to one of us happens to all of us: both for the positive - honor; and for the negative - suffering.  God does not want us divided as believers.  He wants us to care for one another.

Romans 12:10
   Be kindly affectioned one to another with brotherly love; in honour preferring one another;

   We are brothers and sisters in the body of Christ.  As sons and daughters of God, we are to prefer one another and be kindly affectioned one to another as should family members.

Romans 12:15-16
   Rejoice with them that do rejoice, and weep with them that weep.
   Be of the same mind [thoughts] one toward another, Mind not high things, but condescend to men of low estate.  Be not wise in your own conceits.
 
   We are to think the same thoughts about one another.  We are not to exalt ourselves but rather we are to care for one another.

I Peter 3:8
   Finally, be ye all of one mind [thoughts], having compassion one of another, love as brethren, be pitiful, be courteous:

   We are to have compassion toward one another.  That is how we have the same thoughts.

Romans 13:8
   Owe no man any thing, but to love one another; for he that loveth another hath fulfilled the law.

    Jesus Christ left us with one great commandment: love one another.   As members of the body of Christ with Christ as the head we fulfill the law when we love one another.

Romans 14:19
   Let us therefore follow after the things which make for peace, and things wherewith one may edify another.

   To edify is to build up.  We are not to tear each other down.  We are to follow after peace and edify one another.

Romans 15:14
   And I myself also am persuaded of you, my brethren, that ye also are full of goodness, filled with all knowledge, able also to admonish one another.

   Because you are filled with goodness and a knowledge of God's Word you are able to admonish one another.  To admonish one another is to gently remind one another when the other is off the Word.  It must be done in love, out of a heart filled with goodness and with a knowledge of the Word of God.  Remember, first and foremost we are to love one another and edify one another.  We reprove with God's Word in a manner that reflects God's loving kindness.
 
Romans 16:16
   Salute one another with an holy kiss.  The churches of Christ salute you.

   Five times in the Word of God written to the believers we are told to greet one another with a holy kiss.  As believers we are God's holy ones.  We are to treat each other as God has treated us in making us all members of the body of Christ.

   Romans sets the foundational doctrine of how we are members one of another.  How we are to treat one another as members of the body of Christ is set forth throughout the Word of God written to the believers:

Members One of Another: Romans 12:5, I Corinthians 12:25, Ephesians 4:25
Prefer One Another: Romans 12:10
Same Mind One Toward Another: Romans 12:16, Romans 15:5, I Peter 3:8
Love One Another: Romans 13:8, Galatians 5:13, Ephesians 4:2, I Thessalonians 3:12, 4:9, Hebrews 10:24, I Peter 1:22, 3:8, I John 3:11, 3:23, 4:7, 4:11, 4:12
Edify One Another: Romans 14:19, I Thessalonians 5:11
Receive One Another: Romans 15:7
Teach & Admonish One Another: Romans 15:14, Colossians 3:16
Greet One Another: Romans 16:16, I Corinthians 16:20, 2 Corinthians 13:12, I Peter 5:14
Tarry One for Another: I Corinthians 11:33
Serve One Another: Galatians 5:13
Forbear One Another: Ephesians 4:2, Colossians 3:13
Kind One to Another: Ephesians 4:32
Forgive One Another: Ephesians 4:32, Colossians 3:13
Comfort One Another: I Thessalonians 4:18, 5:11
Exhort One Another: Hebrews 3:13, 10:25
Pray for One Another: James 5:16
Use Hospitality One to Another: I Peter 4:9
Minister the gift One to Another: I Peter 4:10
Submit yourselves One to Another: I Peter 5:5
Fellowship One with Another: I John 1:7

The NOTS:

Judge Not One Another: Romans 14:13
Consume Not One Another: Galatians 5:15
Provoke Not One Another: Galatians 5:26
Envy Not One Another: Galatians 5:26
Lie Not One to Another: Colossians 3:9
Prefer Not One Over Another: I Timothy 5:21
Speak Not Evil One of Another: James 4:11
Grudge Not One Another: James 5:9