Psalm 89:35

I have made an oath once by my holy name, that I will not be false to David.

Amos 4:2

The Lord God has taken an oath by his holy name, that the days are coming when they will take you away with hooks, and the rest of you with fish-hooks.

Amos 8:7

The Lord has taken an oath by the pride of Jacob, Truly I will ever keep in mind all their works.

2 Thessalonians 2:13

But it is right for us to give praise to God at all times for you, brothers, loved by the Lord, because it was the purpose of God from the first that you might have salvation, being made holy by the Spirit and by faith in what is true:

Titus 1:2

In the hope of eternal life, which was made certain before eternal time, by the word of God who is ever true;

Hebrews 6:13

For when God made his oath to Abraham, because there was no greater oath, he made it by himself,

Hebrews 6:17

So that when it was God's desire to make it specially clear to those who by his word were to have the heritage, that his purpose was fixed, he made it more certain with an oath;

Treasury of Scripture Knowledge

Summary

Once have I sworn by my holiness that I will not lie unto David.

That i will not lie

Bible References

Once

Amos 4:2
The Lord God has taken an oath by his holy name, that the days are coming when they will take you away with hooks, and the rest of you with fish-hooks.
Amos 8:7
The Lord has taken an oath by the pride of Jacob, Truly I will ever keep in mind all their works.
Hebrews 6:13
For when God made his oath to Abraham, because there was no greater oath, he made it by himself,

That i will not lie

2 Thessalonians 2:13
But it is right for us to give praise to God at all times for you, brothers, loved by the Lord, because it was the purpose of God from the first that you might have salvation, being made holy by the Spirit and by faith in what is true:
Titus 1:2
In the hope of eternal life, which was made certain before eternal time, by the word of God who is ever true;

Basic English, produced by Mr C. K. Ogden of the Orthological Institute - public domain