Jerome of Stridon
One must ready and fortify the countenance and the outstretched hand, so that through both the spoken word and the gestures and stance of the prophet, the encirclement of the city may be signified.
And thou shalt turn thy face to the siege of Jerusalem and thy arm shall be stretched out: and thou shalt prophesy against it.
וְאֶל־מְצ֤וֹר יְרוּשָׁלִַ֙ם֙ תָּכִ֣ין פָּנֶ֔יךָ וּֽזְרֹעֲךָ֖ חֲשׂוּפָ֑ה וְנִבֵּאתָ֖ עָלֶֽיהָ׃
2 Church Fathers comment on this verse
One must ready and fortify the countenance and the outstretched hand, so that through both the spoken word and the gestures and stance of the prophet, the encirclement of the city may be signified.
At the completion of Jerusalem, the Lord speaks to the prophet, saying, You shall set your face steadfastly and strengthen your resolve to prophesy against it. The act of setting one's face reflects righteous anger, while strengthening one's resolve indicates the discipline that will be enforced.
Passages read together with this verse.