More than four years after saying "I do", Jennifer Lopez and Marc Anthony secretly renewed their vows in Las Vegas early Sunday morning, PEOPLE has learned.

Witnessed by two friends, the duo renewed the vows at Caesars Palace's Forum Tower Penthouse at 3:15 a.m. Sunday after a night at Pure Nightclub, a rep for the hotel confirmed to PEOPLE. The service was officiated by Rev. Steven Smith.

"It was totally a spur of the moment thing," a source said. "They decided around 12:30 in the morning that they wanted to do it and started calling for ministers."

The renewal ceremony comes after the couple spent the previous evening club-hopping in Las Vegas and taking in a show. Most in the city believed the couple was in the city to celebrate Anthony's birthday from last month.

"(Marc) said they were in town for his birthday and they wanted to celebrate," said a source who talked to the couple.

On Friday, the couple headed to LAX Nightclub and The Bank after checking out Criss Angel's new Cirque Du Soleil show Believe – all under the guise the couple was in town celebrating Anthony's birthday from last month.

Jennifer Lopez and Marc Anthony Renew Their Vows in Vegas - Jennifer Lopez, Marc Anthony : People.com

Source: Gossip Rocks Forum