Your ears shall hear a word behind you, saying, “This is the way, walk in it.” Isaiah 30:21
I occasionally become frustrated with the book of Isaiah. Like the other Major Prophets, this book is not easily understood and the narrative thread that holds it together is not always in chronological order. Yet, just when I think I have gleaned all from the book that my weak mind can possibly untangle something new, fresh, and precious jumps from the page.
I had memorized and often drawn comfort from Isaiah 30:21, but never before wondered why the voice of God came from behind His people rather than going on before them. Guides are general up ahead forging the way, not lingering behind. When God guided Moses and roughly three million Israelites through the desert into the Promised Land, He went before them as a cloud by day and a column of fire by night.  Jesus said that when He put forth His sheep He would go before them.  Yet, here the voice of God comes from behind.
The answer to that riddle starts way back at the beginning of the chapter.
For much of his book of Isaiah is shouting out to the people telling them the exact nature of their sin. This chapter begins the same. The people are rebellious. The people are headstrong. They are sure they have a plan figured out that will keep them safe, but Isaiah shouts a warning of failure.
In verse fifteen, the tone changes and rather than scolding, the prophet relays the tender, pleading voice of God. “For thus says the Lord God, the Holy One of Israel: ‘In returning and rest you shall be saved; / In quietness and confidence shall be your strength.’” There was a way out. There was safety. But, it was not in the direction that the people were heading. Their safety would be in waiting yet they chose instead to scheme, plan and fight the enemy head on.
What is God’s reaction to this? Isaiah tells us: “Therefore the LORD will wait, that He may be gracious to you.”  Because the people refused to wait on God, the Holy Creator of the Universe would wait instead for them. There will come a day when they would cry out in their trouble, and what will happen then? “He will be very gracious at the sound of your cry; / When He hears it, He will answer you.”  But, because the people had raced ahead with their own plans, when He spoke, they would hear the guiding voice behind them.
No wonder Isaiah calls God’s actions, “very gracious’ . How much more mercy and grace could He show than to both lead the way before us and when we race ahead of His leading, call us from behind? That’s double grace. The kind of grace I often need.
 Exodus 13:22
 John 4:10
 Isaiah 30:18
 Isaiah 30:19