Adam Clarke on 1 Corinthians 14:25

And thus are the secrets of his heart - As these, who were the prophets or teachers, had often the discernment of spirits, they were able in certain cases, and probably very frequently, to tell a man the secrets of his own heart; and, where this was not directly the case, God often led his ministers to speak those things that were suitable to the case before them, though they themselves had no particular design. The sinner, therefore, convinced that God alone could uncover the secrets of his heart, would be often obliged to fall down on his face, abashed and confounded, and acknowledge that God was truly among them. This seems to be the plain meaning of the passages before us.