For when they say the Church don't matter
... A personal favorite:
"These things write I unto thee, hoping to come unto thee shortly. But if I tarry long, I write these things that thou mayest know how thou oughtest to behave thyself in the house of God: which is the church of the living God, the pillar and ground of the truth."
I Timothy 3:14-15
... any other suggestions of Scriptures that establish and defend the significance of the Church?