Albert Barnes Commentary Acts 2:31

"he foreseeing [this] spake of the resurrection of the Christ, that neither was he left unto Hades, nor did his flesh see corruption." — Acts 2:31 (ASV)

He seeing this before... He saw this by the spirit of prophecy. From this it appears that David had distinct views of the great doctrines pertaining to the Messiah.

Spake... See Psalm 16.

That his soul... See Barnes on Acts 2:27.

"Before": or, foreseeing. Spake of the resurrection (1 Peter 1:11–12).