John 3:33

Whoever does accept it has thereby acknowledged that God is true.

John 6:27

You must not work for the food that perishes, but for that which lasts for eternal life, which the Son of Man will give you, for God the Father has authorized him to do so."

Romans 3:3-4

What if some of them have shown a lack of faith? Can their lack of it nullify the faithfulness of God?

Romans 4:18-21

Abraham, hoping against hope, had faith, and so became the father of many nations, in fulfilment of the Scripture, "So countless shall your descendants be."

2 Corinthians 1:18

As surely as God can be relied on, there has been no equivocation about our message to you.

2 Corinthians 1:22

and put his seal upon us and given us his Spirit in our hearts, as earnest-money.

Ephesians 1:13

You also have heard the message of the truth, the good news of your salvation, and believed in him, and through union with him you have been marked with the seal of the holy Spirit that was promised,

Titus 1:1-2

Paul, a slave of God, and an apostle of Jesus Christ, to arouse faith in those whom God has chosen, and the comprehension of religious truth,

Hebrews 6:17

Therefore, God in his desire to make it perfectly clear to those to whom he made his promise, that his purpose was unalterable, bound himself with an oath,

1 John 5:9-10

If we accept the testimony of men, the testimony of God is stronger still; for the value of God's testimony lies in this, that he has testified to his Son.

Revelation 7:3-8

"Do not harm the earth or the sea or the trees until we mark the slaves of our God 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
What if some of them have shown a lack of faith? Can their lack of it nullify the faithfulness of God?
Romans 4:18
Abraham, hoping against hope, had faith, and so became the father of many nations, in fulfilment of the Scripture, "So countless shall your descendants be."
2 Corinthians 1:18
As surely as God can be relied on, there has been no equivocation about our message to you.
Titus 1:1
Paul, a slave of God, and an apostle of Jesus Christ, to arouse faith in those whom God has chosen, and the comprehension of religious truth,
Hebrews 6:17
Therefore, God in his desire to make it perfectly clear to those to whom he made his promise, that his purpose was unalterable, bound himself with an oath,
1 John 5:9
If we accept the testimony of men, the testimony of God is stronger still; for the value of God's testimony lies in this, that he has testified to his Son.