If you’re going to be preaching or teaching on the communion of saints, here’s a great illustration from Thomas Brooks:

Unity is the best bond of safety in every church and commonwealth.  We shall be invincible, if we be inseparable.  And this did the Scythian king in Plutarch represent livelily to this eighty sons.  He, being ready to die, commanded a bundle of arrows fast bound together to given to his sons to break; they all tried to break them, but being bound fast together, they could not; then he caused the band to be cut, and then they broke them with ease.  He applied it thus: ‘My sons, so long as you keep together, you will be invincible; but if the band of union be broken betwixt you, you will easily be broken in pieces.  (Smooth Stones Taken From Ancient Brooks, p.47)