A.T. Robertson Commentary Acts 1:24

"And they prayed, and said, Thou, Lord, who knowest the hearts of all men, show of these two the one whom thou hast chosen," — Acts 1:24 (ASV)

Show us the one whom thou hast chosen (αναδειξον ον εξελεξω). First aorist active imperative of αναδεικνυμ, to show up, make plain. First aorist middle indicative second person singular of εκλεγω, to pick out, choose, select. In this prayer they assume that God has made a choice. They only wish to know his will. They call God the

heart-searcher or

heart-knower (καρδιογνωστα, vocative singular), a late word, here and Ac 15:8 only in the N.T. Modern physicians have delicate apparatus for studying the human heart.