Question: "What does it mean that God put words in your mouth (Isaiah 59:21)?"
Answer: There are several modern idioms that come from passages of the Bible. One such phrase is put words into someone’s mouth, and it comes from and Isaiah 59:21 (see also 2 Samuel 14:3). In Isaiah, the Lord says, “My Spirit, who is on you, will not depart from you, and my words that I have put in your mouth will always be on your lips, on the lips of your children and on the lips of their descendants—from this time on and forever.” God’s promise to put words in the mouths of His children means that they will know God’s Word and speak of it.
Isaiah 59 is a beautiful passage of hope that begins with a lamenting of the current conditions because of sin and the separation of the people from God (Isaiah 59:1–16). Yet God personally resolves the situation (Isaiah 59:16–21), and He explains that as part of the resolution He put words “in your mouth” (Isaiah 59:21).
God is capable of saving and quick to hear (Isaiah 59:1), however, because the people of Israel had violated the covenant God had made with them through Moses, the nation was separated from Him to the extent that He would choose not to hear their requests (Isaiah 59:2). God wasn’t turning a cold shoulder to the people without warning—He had told them clearly and prepared them for those consequences if they broke His covenant (see Deuteronomy 28—30, for example). Because the people had abandoned Him, they were experiencing those consequences. And yet, even in God’s judgment, there was the promised blessing that He would put words “in your mouth” (Isaiah 59:21).
The horrific list of specific failures and indictments of the people is presented in Isaiah 59:3–8, demonstrating clearly that the consequences were earned. But in Isaiah 59:9–15 there is a collective acknowledgement of that sin and a recognition that God was not pleased with their behavior. God could have judged the people without any mercy at all. Yet even in His judgment we see His grace at work.
There was no one among the people who could save them from their sin (Isaiah 59:16), so God accomplished that task Himself, even though He is the mighty and righteous Judge (Isaiah 59:17–19). The Redeemer would come to Zion (Isaiah 59:20). Elsewhere, we find that part of this redemptive promise included a new covenant that God would make with the people of Israel (Jeremiah 31:31–40), and as part of that covenant God would write His law on the hearts of the people, rather than on tablets of stone. There would be no more need for conditional covenants and ethics codes to illustrate His holiness and the people’s need for holiness—He would provide that to them directly, as they would all know Him (Jeremiah 31:34).
In the final verse of Isaiah 59, God refers to the New Covenant, addressing the people and reminding them that His Spirit would be within them and that He would put His words in their mouths (Isaiah 59:21). The Spirit and the words of God would remain forever. Those two great blessings would not be dependent on the people’s own actions, but they would be based on God’s mercy and grace—they would not depart from their offspring or their offspring’s offspring. In other words, once those blessings were provided—when the New Covenant is fulfilled when Jesus returns to install His kingdom (Revelation 20)—they would never end.
Even though this specific promise of redemption is for the people of Israel as part of God’s intended plan to fulfill His covenant promises to Abraham (Genesis 12:2–3), God also promised that He would bring blessings even to those who were not from the physical lineage of Abraham (Genesis 12:3b). In fact, we discover that God brings redemption and salvation to people of every nation, tribe, people, and tongue (Revelation 7:9). So when we read of His promised mercy and grace to Israel, and we look for Him to keep those promises literally and specifically, we can also remember that He promised blessings for all the families of the earth, and we can rejoice that He loves the whole world and has provided the way—through Israel’s Messiah—for us all to have peace with God and eternal life.