Musar zu Jeschijahu 63:9

The fourth - "To the remnant of His inheritance" - behold, the Holy One, blessed be He, acts with His people in this way, to say, "What can I do with Israel, [as] they are My relatives - relation of flesh do I have with them." As they are the spouse to the Holy One, blessed be He; and He calls them, "My daughter" and "My sister," "My Mother" - as they, may their memory be blessed, explained (Shir HaShirim Rabbah 3:11:2). And it is written (Psalms 148:14), "Israel, His close (kerovo) nation" - He has actual closeness (kurvah) with them, and they are His children. And that is [the meaning of] the remnant of (she'erit) His inheritance" - it is an expression of relation (she'er) of flesh; and in the end, they are His (literal) inheritance. "And what shall I say? If I punish them, behold the pain is upon Me; as it is written (Isaiah 63:9), 'In all their distress, the distress (tsar) was to Him.'" And [to Him (lo)] is written with a [letter,] alef, to say that their pain reached the Highest Wonder (Wonder, peleh, being composed of the same letters as the spelling of alef, and representing Keter) - and all the more so, the two Faces through which is the central running [of the world] - but it is written with a [letter,] vav, [to mean that] the distress is to Him. And it is written (Judges 10:16), "and His soul could not bear the travail of Israel" - as He does not bear their pain and their disgrace, because they are "the she'erit [of] His inheritance."