Isaiah 41:6

אִישׁ אֶת־רֵעֵהוּ יַעְזֹרוּ וּלְאָחִיו יֹאמַר חֲזָק׃

6 Each man helped his neighbor. Each said to his brother, "Be strong."

אִישׁ אֶת־רֵעֵהוּ יַעְזֹרוּ Each man helped his neighbor. יַעְזֹרוּ, qal imperfect of עָזַר, "help;" "God will help her at break of day" (Psalm 46:5). The Mp note says that this form occurs only here and in Isaiah 30:7 (again, note that this is a form that occurs rarely, but in both halves of Isaiah).

וּלְאָחִיו יֹאמַר חֲזָק Each said to his brother, "Be strong." חֲזָק qal imperative, masculine singular. Another Mp note tells us that this is a hapax legomenon; note that this is a reference to the form and not the root word (e.g., "The Lord has one who is powerful and strong," Isaiah 28:2). True hapax legomena are fairly uncommon. The more common form of this word is חִזְקוּ (qal imperative, masculine plural; cf. Isaiah 35:3-4).