Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
Christ's resurrection rests on many eye-witnesses, including Paul, and is the great fact preached as the groundwork of the Gospel. They who deny resurrection in general must deny that of Christ; and the consequence will be that Christian preaching and faith are vain.
I declare - literally, 'I make known.' It implies some reproach that it should be now necessary to make it known to them afresh, owing to some 'not having the knowledge of God' (1 Corinthians 15:34: cf. Galatians 1:11).
Wherein ye stand - ye now take your stand. Your present high standing, if ye suffer not yourselves to fall from it.