Romans 7:3

Therefore while the husband lives, she shall be called an adulteress if she is married to another man; but if the husband has died, she is free from the law, so that she is not an adulteress if married to another man.

Matthew 5:32

But I tell you, that whoever puts away his wife, except for adultery, causes her to commit adultery; and whoever marries her that is put away, commits adultery.

Mark 10:6-12

but from the beginning of creation, he made them male and female.

John 8:3-5

And the scribes and Pharisees brought him a woman taken in adultery, and placing her in the midst

1 Timothy 5:11-14

But reject the younger widows; for when they fall into pleasure to the neglect of Christ, they wish to marry,

Treasury of Scripture Knowledge

Summary

So then if, while her husband liveth, she be married to another man, she shall be called an adulteress: but if her husband be dead, she is free from that law; so that she is no adulteress, though she be married to another man.

General references

Bible References

So then

Matthew 5:32
But I tell you, that whoever puts away his wife, except for adultery, causes her to commit adultery; and whoever marries her that is put away, commits adultery.
Mark 10:6
but from the beginning of creation, he made them male and female.
John 8:3
And the scribes and Pharisees brought him a woman taken in adultery, and placing her in the midst

Though

1 Timothy 5:11
But reject the younger widows; for when they fall into pleasure to the neglect of Christ, they wish to marry,

General references

Mark 10:9
What God therefore has yoked together, let not man separate.