Isaiah 41:8

וְאַתָּה יִשְׂרָאֵל עַבְדִּי יַעֲקֹב אֲשֶׁר בְּחַרְתִּיךָ זֶרַע אַבְרָהָם אֹהֲבִי׃

8 But you, O Israel, my servant; O Jacob whom I have chosen, O seed of Abraham My friend;

Following after the initial pronoun, "But you," all of the names in this verse become vocatives (an Mp note points out that the phrase וְאַתָּה יִשְׂרָאֵל occurs only once). In a strong contrast with what has just been said about the pagans and their idols, we now have the other side of things. With true believers, there is no choosing of God the way a craftsman picks out a block of stone. God chose us. In this and the next dozen chapters, through chapter 53, the word "servant" (עַבְדִּי) is going to be an increasingly important word. In some places, God will refer to outsiders as his servant, performing a specific task ("I will send for my servant Nebuchadnezzar," Jeremiah 43:10). Sometimes it may refer to the nation of Israel as a whole, but more and more often it will refer to a specific individual who will perform a specific function in God's plan for saving all mankind: “See, my servant will act wisely; he will be raised and lifted up and highly exalted” (Isaiah 52:13). The choice of using the word "seed" (זֶרַע) of Abraham also recalls the covenant, and the promises of God.

בְּחַרְתִּיךָ is a qal perfect with 2 m sg suffix. The Mp note for this word is somewhat interesting. It simply tells us that בְּחַרְתִּיךָ occurs twice, and in verse 9 בְּחַרְתִּיךָ has the same Mp notation. But that isn't the end of the story, since Isaiah 48:10 also marks the qal perfect 1 sg + 2nd masc sg suffix form בְּחַרְתִּיךָ with an Mp note, but that (identical) form is said to occur three times. In Isaiah 48:10, there is also a textual variant noting that the Isaiah scroll from Qumran (1QIsª) has בחנתיכה "Whom I have examined." This suggests that the Masorete who wrote the notes for 41:8 and 41:9 may have had a Hebrew text closer to the Qumran test than to the MT as we have it now. However, the note at 48:10 corresponds to the text as we have it before us.