The grandmother carried the sleeping infant boy on a white pillow toward the synagogue’s altar, and passed him to her son. Her son carried the infant toward the mohel, or Jewish ritual circumciser, who stood amid a cluster of chanting men.

The mohel lifted the infant’s clothing to expose his tiny penis. With a rapid flick of a sharp two-sided scalpel, the mohel sliced off the foreskin and held it between his fingers. Then he took a sip of red wine from a cup and bent his head. He placed his lips below the cut, around the base of the baby’s penis, for a split second, creating suction, then let the wine spill from his mouth out over the wound.

“You’re O.K.,” he said to the infant, Benjamin Asher Mortob, who stopped crying after several more seconds. The sanctuary filled with elated prayer.

The mohel, A. Romi Cohn, said he had performed more than 25,000 circumcisions, on babies and adults, in New York City and elsewhere over the last 40 years. When he circumcises an infant, he said, he almost always put his mouth on the baby’s penis to pull blood away from the wound in an ancient part of the circumcision ritual, known in Hebrew as metzitzah b’peh, that is still commonplace in parts of the ultra-Orthodox Jewish community but is rare in other branches of Judaism.