I would like to know where in the Bible does it say that the lion will lie down with the lamb?
You are referring to the 1,000 year kingdom of Christ on earth. There are a number of passages in scripture that describe this period of time. Isaiah 11:1-6 says that it arrives sometime after Jesus’ first advent or His birth, death and return to life. It is a time of peace, long life and joy. Here is the passage that almost answers your question.
And the wolf will dwell with the lamb, And the leopard will lie down with the kid, And the calf and the young lion and the fatling together; And a little boy will lead them. (NASB) Isaiah 11:6
Here is another Old Testament passage that is similar.
The wolf and the lamb shall graze together, and the lion shall eat straw like the ox; and dust shall be the serpent’s food. They shall do no evil or harm in all My holy mountain,” says the LORD. (NASB) Isaiah 65:25
However, there are no biblical passages that refer to the lamb and the lion lying down together. That is a very commonly misquoted statement. What is truly amazing about this passage is that a little boy will lead them. Now that is amazing.
Jesus’ Kingdom. The Isaiah passages do not describe heaven – they describe Jesus’ earthly kingdom. We can see this by reading the verses just before the Isaiah 65:25 passage.
And there will no longer be heard in her the voice of weeping and the sound of crying. No longer will there be in it an infant who lives but a few days, or an old man who does not live out his days; For the youth will die at the age of one hundred and the one who does not reach the age of one hundred Shall be thought accursed. And they shall build houses and inhabit them; they shall also plant vineyards and eat their fruit. They shall not build, and another inhabit, they shall not plant, and another eat; for as the lifetime of a tree, so shall be the days of My people, and My chosen ones shall wear out the work of their hands. They shall not labor in vain, or bear children for calamity; for they are the offspring of those blessed by the LORD, and their descendants with them. It will also come to pass that before they call, I will answer; and while they are still speaking, I will hear. (NASB) Isaiah 65:19-24
Notice that children will be born and older men will die. Revelation 20:1-4 describes heaven. It is a very different picture.
And I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea. And I saw the holy city, new Jerusalem, coming down out of heaven from God, made ready as a bride adorned for her husband. And I heard a loud voice from the throne, saying, “Behold, the tabernacle of God is among men, and He shall dwell among them, and they shall be His people, and God Himself shall be among them, and He shall wipe away every tear from their eyes; and there shall no longer be any death; there shall no longer be any mourning, or crying, or pain; the first things have passed away.” (NASB) Revelation 20:1-4
God loves peace. Sin brought war, violence, and hatred. Someday when Jesus reigns on this earth, He will bring a temporary peace. And those who are alive during that time will see real peace – as only God can give. Lord Jesus, come quickly!