Abraham built an altar to express his gratitude and commitment to the Lord ( Genesis 12:8; cf. Joshua 22:34; Joshua 24:26-27), and Jacob erected a pillar when he memorialized God"s covenant to him ( Genesis 28:22). The Egyptians will do these things throughout their land to express those things in that day ( Isaiah 19:19). Israelites during the Judges Period cried out to God because of their oppressors, and He sent them deliverers ( Judges 3:9; Judges 3:15; Judges 6:7; Judges 10:10). Their great oppressor in the past, of course, had been Egypt herself. Similarly, when the Egyptians call out to God for help, He will send them a Savior and a Champion, Messiah ( Isaiah 19:20). The Lord revealed Himself to the Israelites and brought them into a saving relationship with Himself through bitter defeat in the Exodus ( Exodus 7:5; Exodus 9:29; Exodus 14:4). He will do the same to the Egyptians in that future day ( Isaiah 19:21; cf. Jeremiah 31:34; Zechariah 14:16-18), and they will respond with appropriate worship. Parents sometimes strike their children to bring them into line, and God will discipline Egypt to bring her to Himself. He will hurt them, but He will hurt them to heal them, like a surgeon ( Isaiah 19:22). This whole section is a picture of reconciliation still future. [source][source][source]
"This is the point: the worship of Yahweh in Egypt will be open and official.... Historical fulfillment here, like historical fulfillment in each of the five "in that day" passages, did not occur." [1][source]