Matthew 24:35

[Although] the sky and the earth will pass away [See II Pet. 3:10], my words will not pass away [i.e., they will certainly come true].

Hebrews 6:18-20

He did this so that by two unchangeable things [i.e., His promise and His oath], (and it is impossible for God to lie), we, who have fled [to God] for refuge, could be greatly encouraged to take hold of the hope set before us [i.e., the hope of never ending life].

Treasury of Scripture Knowledge

Summary

Thy mercy, O LORD, is in the heavens; and thy faithfulness reacheth unto the clouds.

Bible References

Faithfulness

Matthew 24:35
[Although] the sky and the earth will pass away [See II Pet. 3:10], my words will not pass away [i.e., they will certainly come true].
Hebrews 6:18
He did this so that by two unchangeable things [i.e., His promise and His oath], (and it is impossible for God to lie), we, who have fled [to God] for refuge, could be greatly encouraged to take hold of the hope set before us [i.e., the hope of never ending life].