Hebrews 6 :18

that by two immutable things, in which it is impossible for God to lie, we might have strong consolation, who have fled for refuge to lay hold of the hope set before us. (Hebrews 6:18)

As human beings, we are prone to lying at some point in our lives, because we are not perfect. However, one of the attributes of God is that “He cannot lie”. This is what the writer of Hebrews affirms in chapter 6, based on the example of Abraham that we find in Genesis chapter 15. Let me quote this passage and explain its meaning.

Genesis : 15: 1 – 18  After these things the word of the LORD came to Abram in a vision, saying, “Do not be afraid, Abram. I am your shield, your exceedingly great reward.”

But Abram said, “Lord GOD, what will You give me, seeing I go childless, and the heir of my house is Eliezer of Damascus?”
Then Abram said, “Look, You have given me no offspring; indeed one born in my house is my heir!”

And behold, the word of the LORD came to him, saying, “This one shall not be your heir, but one who will come from your own body shall be your heir.”

Then He brought him outside and said, “Look now toward heaven, and count the stars if you are able to number them.” And He said to him, “So shall your descendants be.”
And he believed in the LORD, and He accounted it to him for righteousness.
Then He said to him, “I am the LORD, who brought you out of Ur of the Chaldeans, to give you this land to inherit it.”
And he said, “Lord GOD, how shall I know that I will inherit it?”

So He said to him, “Bring Me a three-year-old heifer, a three-year-old female goat, a three-year-old ram, a turtledove, and a young pigeon.”
Then he brought all these to Him and cut them in two, down the middle, and placed each piece opposite the other; but he did not cut the birds in two.

And when the vultures came down on the carcasses, Abram drove them away.
Now when the sun was going down, a deep sleep fell upon Abram; and behold, horror and great darkness fell upon him.
Then He said to Abram: “Know certainly that your descendants will be strangers in a land that is not theirs, and will serve them, and they will afflict them four hundred years.
And also the nation whom they serve I will judge; afterward they shall come out with great possessions.
Now as for you, you shall go to your fathers in peace; you shall be buried at a good old age.
But in the fourth generation they shall return here, for the iniquity of the Amorites is not yet complete.”
And it came to pass, when the sun went down and it was dark, that behold, there appeared a smoking oven and a burning torch that passed between those pieces.
On the same day the LORD made a covenant with Abram, saying: “To your descendants I have given this land, from the river of Egypt to the great river, the River Euphrates—

The covenant between God and Abraham was a solemn agreement that involved a ritual of cutting an animal in half. The two parties would walk between the halves, signifying that they would suffer the same fate as the animal if they broke the covenant. This was how covenants were made in ancient times, unlike today where we write them down on paper or digital documents.In Hebrews 6 : 16 “ For men indeed swear by the greater, and an oath for confirmation is for them an end of all dispute”

Since there was no one grater than God , God Himself came down and made a covenant with God.

V:18 – that by two immutable things, in which it is impossible for God to lie, we might have strong consolation, who have fled for refuge to lay hold of the hope set before us.

The covenant between God and Abram was established by God , even though Abraham had to endure a long period of waiting for the realization of that promise.