וְרֹ֤אשׁ אֶפְרַ֙יִם֙ שֹׁמְר֔וֹן וְרֹ֥אשׁ שֹׁמְר֖וֹן בֶּן־רְמַלְיָ֑הוּ אִ֚ם לֹ֣א תַאֲמִ֔ינוּ כִּ֖י לֹ֥א תֵאָמֵֽנוּ׃ (ס)
And the head of Ephraim is Samaria, And the head of Samaria is Remaliah’s son. If ye will not have faith, surely ye shall not be established.’
Rashi on Isaiah
if you do not believe My prophecy, you, Ahaz, and his people, for I know that you are wicked.
Ibn Ezra on Isaiah
And the head of, etc. As I explained.10In the preceding verse כי was explained to signify Although; this verse is the continuation of it, and וכי ראש═וראש And although the head, etc.
Rashi on Isaiah
it is because you cannot be believed There is no truth in you.