Habakkuk speaks with himself, and, mindful of his office, waits for the communication which he confidently ex-poets (Jeremiah 33:3). I will stand upon my watch (Isaiah 21:6, Isaiah 21:8). As a watchman goes to a high place to see all around and discern what is coming, so the prophet places himself apart from men, perhaps in some secluded height, in readiness to hear the voice of God and seize the meaning of the coming event.
Prophets are called "watchmen" (comp. Ezekiel 3:17; Ezekiel 33:2, Ezekiel 33:6; Micah 7:4). The tower; i.e. watch tower, either literally or metaphorically, as in the first clause. Septuagint, πέτραν, "rook."
What he will say unto me; quid dicatur mihi (Vulgate); τί λαλήσει ἐν ἐμοί, "what he will speak in me". He watches for the inward revelation which God makes to his soul (but see note on Zechariah 2:1-13:0).
When I am reproved; ad arguentem me (Vulgate); ἐπὶ τὸν ἔλεγχόν μου; rather, to my complaint, referring to his complaint concerning the impunity of sinners (Habakkuk 1:1-17:18-17). He waits till he hears God's voice within him what answer he shall make to his own complaint, the expostulation which he had offered to God.
There is no question here concerning the reproofs which others levelled against him, or concerning any rebuke conveyed to him by God—an impression given by the Anglican Version.