In the end, it was not necessary. His blood was taken in a process that took about an hour.

The blood was drawn. The antibody-infused plasma — a clear, yellow-orange liquid — was separated from the red blood cells, which were then pumped back into his body through a machine that whirred at his left elbow.

Dr. Planer said that the timing of the donation, at the start of the Jewish holiday, was meaningful.

“In the Jewish Talmud, it says that saving one life is like saving the world,” he said. “And that sort of rings true a little bit.”

While there is no evidence that convalescent-plasma treatments can help with Covid-19, the technique has been used to fight other viruses, including Ebola, influenza and severe acute respiratory syndrome, or SARS.

Enthusiasm for the potential treatment grew after a paper published in the Journal of the American Medical Association on March 27 suggested that a small study of five critically ill patients in China had shown promising results.

“We need to be able to impact this epidemic in real time,” said Dr. David S. Perlin, the chief scientific officer of the Center for Discovery and Innovation at Hackensack Meridian, which includes 16 other New Jersey hospitals in addition to Hackensack University Medical Center.

“We’re living it,’’ he added. “It’s our friends and colleagues and family.”

The National Covid-19 Convalescent Plasma Project is a related effort that began several weeks ago as a clearinghouse for information and a way to match willing plasma donors with hospitals and doctors authorized to perform infusions.