In our study of Isaiah chapter thirty, we look at the fact that the Lord is our strength and help in times of trouble. We look at Judah and Israel's opposite reactions when they were faced with threats from Assyria.
"'Woe to the obstinate children,' declares the Lord, 'to those who carry out plans that are not mine, forming an alliance, but not by my Spirit, heaping sin upon sin; who go down to Egypt without consulting me; who look for help to Pharaoh's protection, to Egypt's shade for refuge.'" NIV translation
Isaiah relays the words of God to the people of Jerusalem speaking of the fact that the northern kingdom (Israel) had formed an alliance with Egypt when faced with threats from Assyria. We see the details of these events in 2 Kings 7 and Isaiah reminds the people that this was not a part of God's plan for His people. He calls them obstinate children because they ignored the warnings of Amos about the coming judgment at the hands of the Assyrians.
They were "heaping sin upon sin" because of the fact that they put their faith (trust) in someone other than God. The reference to Egypt's shade speaks of someone trying to avoid the heat of the day by finding a shade tree. In a sense, when it got hot in Samaria, they went to Egypt to look for their help instead of trusting in the Lord.
"'But Pharaoh's protection will be to your shame, Egypt's shade will bring you disgrace. Though they have officials in Zoan and their envoys have arrived in Hanes, everyone will be put to shame because of a people useless to them, who bring neither help nor advantage, but only shame and disgrace.'" NIV translation
God reminds the people of Jerusalem that Egypt did not protect Israel and save them from the judgment at the hands of the Assyrians. He speaks of shame and disgrace as one that has been found out to be a fraud. The people of the northern kingdom had claimed to be God's people but, when the going got tough, the truth was revealed. This is a reminder that God allows tough times in the lives of His people so that they will grow in their faith (trust) of Him.