הֲכָזֶ֗ה יִֽהְיֶה֙ צ֣וֹם אֶבְחָרֵ֔הוּ י֛וֹם עַנּ֥וֹת אָדָ֖ם נַפְשׁ֑וֹ הֲלָכֹ֨ף כְּאַגְמֹ֜ן רֹאשׁ֗וֹ וְשַׂ֤ק וָאֵ֙פֶר֙ יַצִּ֔יעַ הֲלָזֶה֙ תִּקְרָא־צ֔וֹם וְי֥וֹם רָצ֖וֹן לַיהוָֽה׃
Rashi on Isaiah
Is it to bend Heb. הֲלָכֹף. This ‘hey’ is the interrogative. That is to say, “Perhaps I require bending the head like a fishhook (כְּאַגְמֹן)?” אַגְמֹן is a sort of bent needle with which they catch fish, and they call it ajjm in O.F.
Ibn Ezra on Isaiah
A day for a man to afflict his soul. Repetition of the same idea (a fast) in other words.
Rashi on Isaiah
Will you call this a fast Heb. הֲלָזֶה. An interrogative form. Therefore, the ‘hey’ is punctuated with a ‘hataf-pattah.’