"O Lord, open my lips, and my mouth will tell about your praise." Psalm 51:15
By asking the Lord to open his lips, David showed how difficult it is to offer thanks to God. This is something God demands of us (Psalm 50:14).
Talking about the Lord and thanking him publicly require an extreme amount of courage and strength because the devil is constantly trying to stop people from doing this. If we could see all of Satan's traps, we would know why David prayed for the Sprit's strength and asked the Lord himself to open David's lips. He wanted to tell the devil, the world, kings, princes, and everyone about the Lord.
Many things can keep our lips shut: the fear of danger, the hope of gaining something, or even the advice of friends. The devil uses these ways to stop us from offering thanks to God, as I have often experienced in my life. And yet, at important times, when God's honor was threatened, God stood by me and opened my mouth in spite of the obstacles. The Spirit urges us on, just as Peter says, "We cannot stop talking about what we've seen and heard" (Acts 4:20). The Spirit prays to God for us with many groans (Romans 8:26). Then, the Lord opens our lips to announce his praise.
Whenever Scdriptrue talks about praising God publicly, it's talking about something extremely dangerous. This is because announcing his praise is nothing other than opposing the devil, the world, our own currupt nature, and everything evil. For how can you praise God without first declaring that the world is guilty and codemned? Anyone who condemns the world is asking to be hated and puts himself in a very dangerous situation.
From "Through Faith Alone" (365 devotional readings from Martin Luther). I think "declare your praise" sounds better than "tell about your praise".
In German: "Herr tue meine Lippen auf, dass mein Mund deinen Ruhm verkuendige". The verb "verkuendigen" is more like "proclaim", "herald", not the plain verb "tell".
It was dangerous for Luther, too, to spread the news of Justification by Faith through Christ alone. But this is exactly what it is about: God will not, shall not, be robbed of his honor and praise, which is that he is the giver of all good things, including our entire salvation.