Oy vey!

The government’s key witness in the corruption retrial of Sheldon Silver used Hebrew code to tell the then-Assembly speaker in 2014 that he had been visited by FBI agents who were poking around the powerful politician’s finances, it was revealed in Manhattan federal court Tuesday.

Dr. Robert Taub said he used the phrase “bikur cholim” — a Jewish commandment to visit and extend aid to the sick — to warn Silver that the feds were on his tail.

“I mentioned it to let him know that I had been rendered ill … rendered sick by a visitation,” Taub told the Manhattan federal jury Tuesday.

“He [Silver] asked whether I had told them anything,” Taub said of the 2014 telephone conversation. “I said I didn’t think so.”

It was the last time they ever spoke, Taub said of Silver, who was later arrested and tried for bribery — only to have his conviction overturned on appeal.

Silver, 74, is now being retried in Manhattan federal court over allegations that he sold his office as one of the three most powerful politicians in the state — along with the Senate majority leader and governor — in exchange for $4 million in illegal kickbacks.

A whopping $3 million of those alleged kickbacks came from Taub’s referrals of his cancer study patients to Silver, who then made a cut of money earned on their lawsuit referrals to his firm, Weitz & Luxenberg.

Prosecutors on Tuesday showed the jury emails from Taub that suggested the then-Columbia University cancer doctor secretly disdained Silver and his law firm as part of a dog-eat-dog crowd that merely sought to get rich off mesothelioma, a rare form of cancer caused by exposure to asbestos.

“Boy, the environment for new cases in NY is canine-eat-canine,” Taub wrote in a 2010 email to a mesothelioma advocate.

“Of course they will all be nice to you for the cases, and hate you if they don’t get them,” Taub wrote in a separate email. “I will keep giving cases to Shelly [Silver] because I may need him in the future — he is the most powerful man in New York state.”

Taub, who is cooperating with the government under a non-prosecution agreement, said Tuesday that he had a purely “business relationship” with Silver that consisted of his patient referrals in exchange for Silver’s help with $500,000 in state grants and other favors.

The feeling of quid-pro-quo was so strong, Taub said, he complained about it in emails.

“If he delivers, I am sure it will cost me,” Taub wrote in a 2011 email to a woman who, along with Taub, was seeking Silver’s help obtaining permits for a race to benefit mesothelioma.

“He [Silver] is very good at getting people to owe him,” Taub said.

“The referrals were the basis of our relationship,” Taub told the Manhattan federal jury. “I believed that if I stopped the referrals, this might cause him to stop those activities,” he said of Silver’s efforts to help patients with the rare form of cancer caused by asbestos.

On cross-examination, Silver’s attorneys questioned Taub about whether Silver had ever explicitly asked for anything in exchange for Taub’s lucrative referrals.

“The understanding was that I felt he wanted the cases that would be referred to Weitz & Luxenberg to go through him in order to incentivize him to become an advocate” for people with mesothelioma, Taub said.

“That’s what you thought, right?” attorney Michael Feldberg asked.

“Yes,” Taub responded.

“Did you know what Shelly thought?”

“I did not discuss it with him, no.”