Romans 12:4,5 "For as in one body we have many members, and the members do not all have the same function, so we, though many are one body of Christ, and individually members one of another." We see that we are members of one body and each member has a different function and by being connected to the body of Christ, makes us connected to each other. The apostle Paul said in Philippians 2:2 "complete my joy by being of the same mind, having the same love, being in full accord and of one mind." Even though we are individuals, we are called to be united in our faith.
The unity of spirit and mind is needed to make we, who are the body of Christ to grow. Ephesians 4:15,16 "....we are to grow up in every way into him who is the head, into Christ, from whom the whole body, joined and held together by every joint with which it is equipped, when each part is working properly, makes the body grow so that it builds itself up in love." Psalm 133:1 Behold, how good and pleasant it is when brothers dwell in unity. (ESV)