Mark 6:18

For John had been saying to Herod, “It is not lawful [under Mosaic Law] for you to have your brother’s wife.”

Leviticus 18:16

You shall not uncover the nakedness of your brother’s wife; it is your brother’s nakedness.

Leviticus 20:21

If a man takes his brother’s wife, it is a hated and unclean thing; he has uncovered his brother’s nakedness. They will be childless.

1 Kings 22:14

But Micaiah said, “As the Lord lives, I will speak what the Lord says to me.”

Ezekiel 3:18-19

When I say to the wicked, ‘You will certainly die,’ and you do not warn him or speak out to tell him to turn from his wicked way to save his life, that same evil man will die in his sin, but you will be responsible for his blood.

Matthew 14:3-4

For Herod had John arrested and bound him and put him in prison [at the fortress of Machaerus, east of the Jordan, to keep him away] because of Herodias, the wife of his brother Philip,

Acts 20:26-27

For that reason I testify to you on this [our parting] day that I am innocent of the blood of all people.

Acts 24:24-26

Several days later Felix came with his wife Drusilla, who was a Jewess. He sent for Paul and listened to him talk about faith in Christ Jesus.

Treasury of Scripture Knowledge

Summary

For John had said unto Herod, It is not lawful for thee to have thy brother's wife.

General references

Bible References

It is

Leviticus 18:16
You shall not uncover the nakedness of your brother’s wife; it is your brother’s nakedness.
Leviticus 20:21
If a man takes his brother’s wife, it is a hated and unclean thing; he has uncovered his brother’s nakedness. They will be childless.
1 Kings 22:14
But Micaiah said, “As the Lord lives, I will speak what the Lord says to me.”
Ezekiel 3:18
When I say to the wicked, ‘You will certainly die,’ and you do not warn him or speak out to tell him to turn from his wicked way to save his life, that same evil man will die in his sin, but you will be responsible for his blood.
Matthew 14:3
For Herod had John arrested and bound him and put him in prison [at the fortress of Machaerus, east of the Jordan, to keep him away] because of Herodias, the wife of his brother Philip,
Acts 20:26
For that reason I testify to you on this [our parting] day that I am innocent of the blood of all people.
Acts 24:24
Several days later Felix came with his wife Drusilla, who was a Jewess. He sent for Paul and listened to him talk about faith in Christ Jesus.

General references

Matthew 14:4
for John had said to him, “It is not lawful (morally right) for you to have her [living with you as your wife].”
Luke 3:19
But when Herod [Antipas] the tetrarch was repeatedly reprimanded [and convicted by John’s disapproval] for having Herodias, his brother’s wife [as his own], and for all the wicked things that Herod had done,