KJV:
But if I tarry long, 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.
NASB:
but in case I am delayed, I write so that you will know how one ought to conduct himself in the household of God, which is the church of the living God, the pillar and support of the truth.