Faith has played a large part in Chris Pratt and Katherine Schwarzenegger's relationship

Chris Pratt and Katherine Schwarzenegger‘s shared religious faith helps keep their relationship strong.

The couple announced their engagement on Sunday with a touching Instagram post, in which Pratt noted the importance of religion in their lives together.

“Sweet Katherine, so happy you said yes! I’m thrilled to be marrying you. Proud to live boldly in faith with you,” Pratt captioned a photo of himself cuddling up to Schwarzenegger, whose engagement ring was front and center.

From the start, faith has played a large part in their relationship. A source previously told PEOPLE that Pratt was initially attracted to Schwarzenegger’s strong spirituality.

“They’re very compatible and have a lot in common,” said the source. “Family is very important to both of them, as well as their spirituality.”

Since the summer, the couple has been spotted going on multiple church dates together. Just one month after they started dating in June, Pratt, 39, and Schwarzenegger, 29, were seen sharing a sweet kiss after attending a church service with the actor’s son Jack.

Credit: Jason Merritt/Getty; Imeh Akpanudosen/Getty

A source adds to PEOPLE that the couple “click on a lot of levels, but definitely on a spiritual level.”

“They have the same outlook on the world, and their faith ties them together,” says the source. “He’s really impressed that she’s vocal and unashamed about her beliefs in God, because that’s how he is. He’s constantly around other people who have no faith or are apologetic about it, but not her. She is willing to talk about it to anyone who will listen.”

Pratt has long been open about his faith, expressing his belief in God at awards shows and on social media. The actor previously said he feels “called” to talk about it.

“That kind of message, it might not be for everybody. But there is a group of people for whom that message is designed,” he said during an interview with the Associated Press. “And nothing fills my soul more than to think that maybe some kid watching that would say, ‘Hey, I’ve been thinking about praying. Let me try that out.’ ”

“That’s the only way I feel like I can repay what has essentially been a giant gift in my life,” he added.

Schwarzenegger, meanwhile, was raised Catholic but has attended nondenominational Christian churches with her family, including brother Patrick Schwarzenegger and mom Maria Shriver, over the years.

She has also been open about discussing her beliefs on social media, often quoting religious text and verses.

In November, Schwarzenegger shared a photo of a sunset with the caption, “God shot.”