DEERFIELD BEACH, Florida (CNN) – Joe Biden gave a fiery speech designed to reassure Jewish voters of Barack Obama’s support of Israel.

“I give you my word as a Biden, I would not have given up (my) job to be Barack Obama's vice president if I didn't in my gut and in my heart and in my head know that Barack Obama is exactly where I am on Israel,” he said.

On an earlier trip to Boca Raton, Florida, Obama himself confronted Internet rumors that he is Muslim and anti-Israel. Obama is a Christian.

“I want to just repeat this because I know that there’s a lot of rumor mongering going around. People have been getting e-mails non-stop,” Obama told a crowd at a synagogue in May.

“That’s why I reject the attempts by some of my opponents in this campaign to distort my position…. As president, I will do everything in my power to help Israel protect itself from these and other threats.”

On Tuesday, Biden also addressed the “scurrilous” e-mails.

“There's some scurrilous stuff going around in the internet, particularly in Florida,” Biden said. “The extent you trust me and understand where my heart is, I promise you, the stuff you're getting on the Internet is simply not true.”

The senator spoke emotionally of taking his sons to the Dachau concentration camp in Germany, telling the crowd he took them because “as every generation passes, it’s harder and harder and harder to understand the enormity, the enormity, of the outrageous things that were committed,” Biden said. “And even it’s harder for people to understand that if we remain silene there is no — no guarantee it won’t happen again.”

Biden peppered his speech with Yiddish words, telling the audience soon they’d be “mishpokhe,” or family, and calling himself a “zayde,” or grandfather.