What do you understand by "the communion of saints"?

First, that all and every one, who believes, being members of Christ, are in common, partakers of him, and of all his riches and gifts; (a) secondly, that every one must know it to be his duty, readily and cheerfully to employ his gifts, for the advantage and salvation of other members. (b)

(a) 1 John 1:3 That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ. 1 Cor.1:9 God is faithful, by whom ye were called unto the fellowship of his Son Jesus Christ our Lord. Rom.8:32 He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things? 1 Cor.12:12 For as the body is one, and hath many members, and all the members of that one body, being many, are one body: so also is Christ. 1 Cor.12:13 For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit. 1 Cor.6:17 But he that is joined unto the Lord is one spirit. (b) 1 Cor.12:21 And the eye cannot say unto the hand, I have no need of thee: nor again the head to the feet, I have no need of you. 1 Cor.13:1 Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal. 1 Cor.13:5 Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil; Philip.2:4 Look not every man on his own things, but every man also on the things of others. Philip.2:5 Let this mind be in you, which was also in Christ Jesus: Philip.2:6 Who, being in the form of God, thought it not robbery to be equal with God: Philip.2:7 But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men: Philip.2:8 And being found in fashion as a man, he humbled himself, and became obedient unto death, even the death of the cross.