Isaiah 40:28

הֲלוֹא יָדַעְתָּ אִם־לֹא שָׁמַעְתָּ אֱלֹהֵי עוֹלָם יְהוָה בּוֹרֵא קְצוֹת הָאָרֶץ לֹא יִיעַף וְלֹא יִיגָע אֵין חֵקֶר לִתְבוּנָתוֹ׃

28 Don't you know? Haven't you heard that the everlasting God, the LORD, the Creator of the ends of the earth does not tire or become weary, and his understanding is unsearchable.

הֲלוֹא יָדַעְתָּ אִם־לֹא שָׁמַעְתָּ Don't you know? Haven't you heard? When אִם occurs in a parallel statement like this one or in a series, it echoes the first interrogative הֲלוֹא in a continuative fashion, perhaps along similar lines as a waw-consecutive used as a continuation of the action of a previous verb.

אֱלֹהֵי עוֹלָם יְהוָה בּוֹרֵא קְצוֹת הָאָרֶץ  that the everlasting God, the LORD, the Creator of the ends of the earth, בּוֹרֵא is a qal active participle, used as an attributive title, "Creator." In the accented text, עוֹלָם is followed by the stroke paseq: עוֹלָ֤ם׀. Although this looks like the accent legarmeh, there are no cases in the Bible of legarmeh being formed with the arrow-shaped mahpak (legarmeh is almost always a combination of munach with paseq). The force of the accent here is slightly separate the Tetragrammaton from the title "Everlasting God," to that there are in effect three Divine titles here. The paseq insures that we will take "everlasting" with "God" (which is also in the construct state) rather than with LORD even though theologically it could go either way. This is an illustration of the five standard rules that govern the paseq line in all its 480 or so occurrences:
   (1) Dividing identical letters that end one word and begin another.
   (2) Between identical or similar words
   (3) Between words that are absolutely contradictory
   (4) Between words that should not be connected grammatically
   (5) Between heterogeneous terms (such as one title with two possible names that fit the title.

לֹא יִיעַף וְלֹא יִיגָע he does not tire or become weary, The qal imperfects show constant attributes of God. יָעַף "become tired" is synonymous with יָגַע "become tired, weary." Perhaps there was a nuance to these words that slightly separated them, but they appear to mean the same thing.

אֵין חֵקֶר לִתְבוּנָתוֹ׃  and his understanding is unsearchable. חֵקֶר is a noun, "the object of searching." Perhaps "quarry" would serve for some people as a definition. A lamed of reference carries meaning of the line into this: There is no point in making an understanding of the Lord's ways the object of your search. Just because the temple would be destroyed doesn't mean that God was no longer going to be looking after his people. We don't need to understand God to love him, or to be loved by him.