According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
Grace ... given unto me (1 Corinthians 3:5). Paul puts this first, to guard against usurping a particle of the divine glory in pronouncing himself "a WISE master-builder."
Wise - i:e., skillful. His skill is shown in laying the foundation (1 Corinthians 2:2). The unskillful builder lays none (Luke 6:49). Christ is the foundation (1 Corinthians 3:11).
Another - whoever comes after me. He does not name Apollos, for he speaks generally of all successors. His warning, "Let every man (especially, though not exclusively, every teacher) take heed how," etc., refers to other successors than Apollos, who doubtless did not build wood, hay, etc., on the foundation (cf. 1 Corinthians 4:15). Believers, too, have to take heed what superstructural doctrine they build upon Christ in themselves and in those whom they influence.
How - with what material: how far wisely, and in builder-like style (1 Peter 4:11).
Buildeth thereupon. Here the superstructure raised on Christ is not, as in Ephesians 2:20-21, of believers, the "lively stones" of the Church (1 Peter 2:5), but the doctrinal and practical teaching which succeeding teachers added to Paul's first teaching; not that they taught what was false, but their teaching was subtle and speculative, rather than solid and simple.