We were going on vacation—me and Eliana, my 18-year-old daughter, and my friend Shira and her 18-year-old daughter, Ruthie. It would be a gift to our daughters, good friends. I booked a cheap charter vacation in Rhodes.

Then I read online reviews. “The beach is nothing to get excited about,” was one. “You have to cross a very busy road to get there and the beach is extremely rocky. The nicer sandy beaches are on the other side of the island.”

I was not too upset because we all agreed we could always take a taxi or rent a car to travel to nicer beaches.

The first morning, Shira and I rose early to go to the beach. We had to cross a two-lane highway—not the six-lane one we had imagined. At the beach, we walked along the rocky shoreline until we found a wonderful spot. It was private and there were chaise lounges. There was a beautiful hotel nearby but the beach was deserted.

We took off our shoes to swim and the rocks cut into our feet. Still, we were able to swim beyond the rocks and enjoy the crystal blue water of the Aegean Sea.

“Let’s try lying on the rocks,” said Shira, a massage therapist. We carefully placed ourselves over the hot rocks. Some were shaped like fists; others were flat like the palm of a hand; they were speckled gray, brown and white. Slowly we rolled from side to side and let them dig into our stiff bodies. Then we gathered some of them to put on our sore shoulders and tired legs, our outstretched arms. We favored the dark, heat-absorbing rocks. Next, I lay on the chair and Shira rolled, prodded and poked me with the rocks. It was extraordinary.

Here I turn to a painful subject—and why rocks are not on the top of my list of favorite things: My son Koby was beaten to death with rocks by terrorists near our home in Israel when he was 13. So my enjoying a hot rock massage—feeling so relaxed and at peace—was surprising.

After our trip, I told the story to a group of high school girls who attend Camp Koby, the summer camp my husband and I created for Israeli children whose loved ones were also killed by terrorists. I mused that when tragedy strikes, the good is almost impossible to see; we only feel the pain.

In Psalms 118:22, we read: “The stone the builder rejected has become the cornerstone.” What is most despised can sometimes become the place from where we build and find joy. I told them how I had been able to transform something difficult into a good thing. In Rhodes, those sharp rocks became tools of healing.

One girl, whose brother was murdered, said, “Once I was walking in a field and I fell and I could see sparks coming out of the rocks. Sometimes to make a fire you have to rub two sticks together. There is also a rock, flint, that has a spark.”

Everything has a spark of God in it, says the Kabbala. And our job in the world is to gather those sparks. Maybe that’s why Shira and I brought back rocks in our suitcases. A few sit on my windowsill. Shira uses hers in her practice. Mine remind me of the joy of that beautiful beach and the turquoise sea.

One day, our faith teaches, God’s goodness will be as clear as those pure, crystal waters.