Deuteronomy 18:21

And if you say {to yourself}, 'How can we know the word that Yahweh has not spoken to him?'

1 Thessalonians 5:24

The one who calls you [is] faithful, who also will do [this].

1 John 4:1-3

Dear friends, do not believe every spirit, but test the spirits [to determine] if they are from God, because many false prophets have gone out into the world.

Revelation 2:2

'I know your works, and your labor and patient endurance, and that you are not able to tolerate evil, and you put to the test those who call themselves apostles and are not, and you found them [to be] false.

Treasury of Scripture Knowledge

Summary

And if thou say in thine heart, How shall we know the word which the LORD hath not spoken?

Bible References

General references

1 Thessalonians 5:24
The one who calls you [is] faithful, who also will do [this].
1 John 4:1
Dear friends, do not believe every spirit, but test the spirits [to determine] if they are from God, because many false prophets have gone out into the world.
Revelation 2:2
'I know your works, and your labor and patient endurance, and that you are not able to tolerate evil, and you put to the test those who call themselves apostles and are not, and you found them [to be] false.