The burial took place in the city of Safed, which is an ancient town located in the northern part of the country. The couple was seen wearing white and surrounded by a large group during the outdoor ceremony.
According to ancient practice, wearing white is believed to attract positive energy.
Ashton wore a long-sleeve shirt and baggy white pants and topped the outfit off with a baseball cap to cover his head throughout the religious service.
Meanwhile, his girlfriend was spotted wearing a white tank top and matching skinny jeans.
The two held onto one another as they stood through the emotional service.
At one point, Mila appeared to be crying and Ashton comforted her by hugging and wrapping his arms around her.
Ashton also put his arms around fellow funeralgoers next to him during a prayer. Rabbi Berg was the founder of the Kabbalah Center in Los Angeles, which has been frequented by Ashton, ex-wife Demi Moore, Madonna and even Britney Spears years ago.
The religious leader passed away on Monday at the age of 86.
"The Rav has left us with incredible knowledge through thousands of hours of teaching, examples of courage that we will never forget, and the comfort of a Kabbalah Centre that we can all call home," read an official statement on Kabbalah website.