Romans 7:3

So then, if during her husband lifetime, she unites herself with another man, she will be counted an adulteress; but if her husband dies, she is free from the Law, so that she is no adulteress, even if she unites herself with another man.

Matthew 5:32

But I tell you that anyone who divorces his wife, except on the ground of unchastity, makes her an adulteress, and whoever marries her when so divorced, commits adultery.

Mark 10:6-12

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

John 8:3-5

when the Scribes and Pharisees had brought a woman who had been caught in the act of adultery. They made her stand in the middle of the court, and said to him.

1 Timothy 5:11-14

But exclude from the list the younger widows; for where they have become wanton against Christ, they desire 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 anyone who divorces his wife, except on the ground of unchastity, makes her an adulteress, and whoever marries her when so divorced, commits adultery.
Mark 10:6
but from the beginning of the creation God made them male and female.
John 8:3
when the Scribes and Pharisees had brought a woman who had been caught in the act of adultery. They made her stand in the middle of the court, and said to him.

Though

1 Timothy 5:11
But exclude from the list the younger widows; for where they have become wanton against Christ, they desire to marry,

General references

Mark 10:9
What therefore God has joined together, let not man put asunder."