The book of Hebrews states something interesting regarding promises God has made in which he will not lie.
17 To those who were to receive what he promised, God wanted to make it very clear that he would never change his purpose . . . 18 There are these two things (the NKJV and other translations have 'two immutable things'), then, that cannot change and about which God cannot lie. (Hebrews 6:17 - 18)
These two things involve the true hope that only Christians possess. The writer of Hebrews takes the next two chapters to explain in detail these two immutable (unchangeable) things.
Notice that Hebrews 7 deals with the greatness of the Melchizedek priesthood as opposed to the Aaronic priesthood. The hope for Israel was to be a great physical nation that would lead all nations to keep the commandments so they would have great physical blessings.
The oath of God, however, was to bring in a better hope - the awesome hope of eternal life as a member of his family inheriting the earth. This is one of the immutable things that will be accomplished in spiritual Israel.
Now, this is the covenant that I will make with the people of Israel . . . I will be their God, and they will be my people. (Hebrews 8:10)
However, what is the second immutable thing?
"The Lord swore and will not revoke His word, 'You are a Priest forever according to the order of Melchisedec. (Melchizedek)' "
. . . but by the word of the swearing of the oath, which supersedes the law, the Son, Who has been perfected forever, has been made High Priest. (Hebrews 7:21, 28, HBFV)
Our Creator has decided that he will not lie because he has sworn to do two things. He first has sworn to make us (humans) into his very kind of people, to make us fully into his own image and likeness as he stated in Genesis 1:26. The second thing he promises is that Jesus will accomplish his ultimate purpose for us through the office of High Priest.
One of the seven things that the Eternal HATES is someone who lies (Proverbs 6:17). In fact, he will ultimately destroy liars (Psalm 5:6). Those who do not repent of lying will be killed forever in the lake of fire (Revelation 21:8). The choice made to not lie is mentioned in several Biblical verses.
29 Israel’s majestic God does not lie or change his mind. (1Samuel 15:29)
. . . God, who does not lie, promised us this life (eternal life) before the beginning of time, (Titus 1:2)