Andra Day Speaks in Tongues When She Prays, Which Helped Her Improvise a Scene in The Deliverance (Exclusive)

Andra Day’s connection with God helped her performance in The Deliverance, she tells PEOPLE.

In the new horror movie directed by Lee Daniels, the actress and singer, 39, plays Ebony Jackson, an alcoholic single mother struggling to support her three children and her own mother Alberta (Glenn Close), with whom she has a difficult relationship.

After moving into a new house, Ebony’s kids become possessed by demons—and she must seek help from the religious world that she had long ago shunned.

In one climactic scene, while battling a demon, Ebony calls on Jesus and begins to speak in tongues when she prays. For that moment in the movie, Day was truly praying, allowing her to actually speak in tongues — i.e., reciting an unknown language in what she calls “an act of worship.”

“I don't know how to explain it, but speaking in tongues is sort of speaking in a heavenly language,” explains Day, who says she doesn’t do it “all the time.”

It’s something that the Oscar-nominated star, who won a Golden Globe for her performance in The United States vs. Billie Holiday, learned to do over the course of her life, she says.

“When I was younger, I was really afraid of [it] and uncomfortable,” recalls the San Diego native, who remembers going to her friend’s house when she was a kid and seeing her friend’s mom speak in tongues. “I was like, ‘This is insane.’ ”

“But then I got older and my relationship with God just kept growing and growing. I just was reading about speaking in tongues. I read about this pastor who struggled with it too. He said it was very weird for him and he just committed himself to it daily,” she continues.

“I remember telling God, I was like, ‘I want that closeness with you. I want that heavenly language.’ So I kept doing it and kept doing it. It still felt weird, it felt weird, felt weird for a year. Then finally one time I really felt the spirit take over. Then it was like, ‘Wow,’ ” says Day.

“I would get clarity in that space,” she says. “I would just hear things about what I'm supposed to do, the people I'm supposed to work with, where I'm supposed to work.”

Day says she didn’t want to act in the scene, but would rather pray and “just let that happen,” she says. Daniels agreed. “Of course, he was like, ‘That’s what I want.’ It has to stay authentic.”

At one point while she was filming the scene, she says producers wondered if they should stop her. “And Lee said, ‘No, just let her go. Lee had the foresight to capture it.”

The Deliverance is in theaters today and streaming on Netflix Friday, Aug. 30.

For more on Andra Day, pick up the new issue of PEOPLE.