John 3:33

The person who has accepted Jesus' testimony has confirmed this [fact], that God is truthful.

John 6:27

Do not work for the [kind of] food that spoils, but for the kind that lasts until never ending life. The Son of man will give you this [kind of food], for God the Father has placed His seal [of approval] on Him."

Romans 3:3-4

But what if some [of the Jews] were unfaithful? Does their lack of faith nullify the faithfulness of God? Certainly not!

Romans 4:18-21

Abraham hoped for what he believed [God had promised], even when there seemed little hope [of it happening], so this made him forefather of many nations, according to the words spoken to him [Gen. 15:5], "Your descendants will be many."

2 Corinthians 1:18

But just as certainly as God is dependable, our message to you is not [both] "yes" and "no" [at the same time].

2 Corinthians 1:22

He has placed His seal of ownership upon us by giving us the down payment of the Holy Spirit [to live] in our hearts.

Ephesians 1:13

You [Gentiles] also, who are in Christ, after having heard the message of truth, the good news about your salvation, and [after] believing in Him, were sealed [i.e., as evidence of ownership] with the promised Holy Spirit. [or, "the Holy Spirit who brings promises"].

Titus 1:1-2

[This letter is from] Paul, a slave of God, and an apostle for [the benefit of] the faith of God's elect [i.e., His chosen people] and [to spread] the knowledge of the truth which leads to godliness,

Hebrews 6:17

Since God wanted to show conclusively to those who would inherit the promise [i.e., Abraham and all of his spiritual descendants], how unchangeable His purpose was, He confirmed it with an oath.

1 John 5:9-10

If we [are willing to] accept the testimony of people about matters, [surely we ought to accept that] the testimony of God is more reliable; because the testimony of God is that He has presented [confirming] testimony concerning [the identity and mission of] His Son.

Revelation 7:3-8

saying, "Do not harm the land, or the ocean, or the trees, until we have sealed the servants of our God [with a mark] on their foreheads."

Treasury of Scripture Knowledge

Summary

He that hath received his testimony hath set to his seal that God is true.

Bible References

Hath set

Romans 3:3
But what if some [of the Jews] were unfaithful? Does their lack of faith nullify the faithfulness of God? Certainly not!
Romans 4:18
Abraham hoped for what he believed [God had promised], even when there seemed little hope [of it happening], so this made him forefather of many nations, according to the words spoken to him [Gen. 15:5], "Your descendants will be many."
2 Corinthians 1:18
But just as certainly as God is dependable, our message to you is not [both] "yes" and "no" [at the same time].
Titus 1:1
[This letter is from] Paul, a slave of God, and an apostle for [the benefit of] the faith of God's elect [i.e., His chosen people] and [to spread] the knowledge of the truth which leads to godliness,
Hebrews 6:17
Since God wanted to show conclusively to those who would inherit the promise [i.e., Abraham and all of his spiritual descendants], how unchangeable His purpose was, He confirmed it with an oath.
1 John 5:9
If we [are willing to] accept the testimony of people about matters, [surely we ought to accept that] the testimony of God is more reliable; because the testimony of God is that He has presented [confirming] testimony concerning [the identity and mission of] His Son.