The day his son was born was the day David Rosenzweig decided to become a bar mitzvah.

Until then, he had never given the matter much thought.

"The moment Josh was born my world changed. I suddenly realized how important it was to establish some bond to our history. I had to reach back and complete my connection to my father — and with every generation," he said.

Two months ago, 47-year-old Rosenzweig finally celebrated his bar mitzvah in a double ceremony with 13-year-old Josh. Reading from the same Torah portion and delivering individual commentary to an audience of 180, father and son united in marking Alameda Temple Israel's first intergenerational b'nai mitzvah.

"It was really very moving to witness the affirmation of the two generations," recalled Temple Israel's Rabbi Patricia Karlin-Neumann.

But no one was more moved than Josh, an only child who said he was thrilled to share his big day with his father because celebrating a bar mitzvah "was something Dad never got the chance to do when he grew up."

Raised by a Christian mother and Jewish father in a small Ohio town, Rosenzweig was brought up "mostly Christian" but made a conscious decision to steer his adult life toward Judaism.

He said he always felt more drawn to his Jewish roots and when he met his wife, Tara, who is Jewish, his decision to embrace Judaism was further reinforced. Yet, although he had a Jewish wedding and has since led a Jewish life, the prospect of a bar mitzvah held little appeal.

Until Josh came along, that is.

"I could never have done it without Josh. He was wonderful and very supportive. He even helped me with my Hebrew, which, until last year, I didn't know how to read."

A recruiting and employment specialist, Rosenzweig explained that he began taking Hebrew lessons in his "spare time" in May 1995.

But there was never any question over whether Josh would celebrate a bar mitzvah.

"I always knew I would have one, ever since I was in first or second grade," the youngster said. "But I only found out about my dad wanting to have one last year."

Despite having attended Hebrew school for years, Josh admitted that he had never really liked attending synagogue before celebrating his bar mitzvah. "Now that I don't have to go, I want to. I even started going to Friday-night services with my family."

Rosenzweig noted that few chances arise during a lifetime for a person to stand before a congregation of family and friends.

"In ancient times the gathering of family and community to celebrate holidays and special events was a common, almost everyday occurrence," he said.

What made the day particularly meaningful to Tara Rosenzweig was watching her husband's 93-year-old father "beaming" from the front row, with tears in his eyes.

"I was also crying. That was something I just never expected. I was shocked at how much we all cried."

Despite having grown up in "Jewish New York," she said she had never felt more Jewishly connected than during the b'nai mitzvah of her husband and son.

"I keep copies of David's bar mitzvah speech in my daytimer at work. And I still look at it every day."

"The whole experience was really tremendous, almost overwhelming," said Rosenzweig. "Before the bar mitzvah I was like a man without a country. I feel like I have finally come full circle."