Luke 16:16 is sometimes used as a proof-text for Sola Scriptura. The argument is that John the Baptist was the final prophet simpliciter. However, the text does not teach this; instead, John was the final Old Testament prophet. As one scholar put it rather succinctly:
John, who in Luke is described as
the last of the prophets of the old epoch (16.16) . . . (Ulrich W. Mauser, Christ
in the Wilderness [Studies in biblical Theology First Series No. 39;
London: SCM Press, 1963; repr., Eugene, Oreg.: Wipf and Stock, 2009], 148)
Further, there were true prophets after John the Baptist. Commenting on a related text (Heb 1:1-2), one Protestant wrote "But we know, as it turns out, that there were prophets after the Son came (Acts 11:27; 13:1; 15:32; 21:10; 1 Cor. 12:28-29; 14:29, 32, 37; Eph. 2:20; 3:5; 4:11)." For more, see my full-length critique of Sola Scriptura:
Not By Scripture Alone: A Latter-day Saint Refutation of Sola Scriptura
