Leviticus 20:19
"And thou shalt not uncover the nakedness of thy mother’s sister, nor of thy father’s sister: for he uncovereth his near kin: they shall bear their iniquity."
Cross References (ranked by relevance)
Leviticus 18:6
None of you shall approach to any that is near of kin to him, to uncover their nakedness: I am the LORD.
Exodus 6:20
And Amram took him Jochebed his father’s sister to wife; and she bare him Aaron and Moses: and the years of the life of Amram were an hundred and thirty and seven years.