He has become known as the Magnificent Mohel, a Chabad rabbi working in Ukraine who this week celebrated an astonishing landmark - 4,500 circumcisions which he has carried out in the last 13 years.
Rabbi Yaacov Gaissinovitch, 35 and a qualified urologist, has been based in Donetsk, Ukraine, since 1998. Moscow-born, he moved with his family to Israel in 1993. The rabbi, who speaks fluent English, Hebrew and Russian, said that he had become ba'al teshuvah - adopting a strictly Orthodox lifestyle - after his move to Israel, and after he attended a Jerusalem yeshivah, had learned how to perform a brit milah.
Speaking on his way to the northern Ukrainian city of Lutsk, to perform yet another brit, Rabbi Gaissinovitch added: "After I specialised under some of Israel's most famous mohels, I myself was ordained to be a mohel.
"A short time later I was asked by the 'Brit Yosef Yitzchak' organisation, which provides circumcision services to any Jew worldwide, to be their emissary in Ukraine. I arrived here in 1998 and started working as the only mohel for Ukraine and Moldova."
Since then, it's not just the Ukrainian Jewish birthrate which has kept Rabbi Gaissinovitch busy. Many adults who have rediscovered their Jewish roots, and quite a few more who have converted to Judaism, have turned to the rabbi for his circumcision services. Sometimes, he says, he has needed to perform up to five circumcisions in a single day.
But his extraordinary record includes "22 circumcisions in a single day, and 36 circumcisions in two days, that I made in a Jewish camp in Dnepropetrovsk". The "patients" were Jewish campers "who volunteered to undergo the procedure with their parents' permission".
A regular week for the Magnificent Mohel is a dizzying calendar of flights and ceremonies.
"Last week I did a circumcision in Dnepropetrovsk, which is 300km from Donetsk, and then came back to Donetsk. On Monday morning I flew to Moscow, then to Nalchik in the Caucasus area to do a circumcision for a baby, then back to Moscow, to Donetsk and immediately on to Kiev and to Odessa, and in each place I did a circumcision.
"Today at 7am I already did a circumcision in Donetsk, then I flew to Kiev and now I'm on the way to Lutsk, 500km away, to perform another one.
"After that I will fly back to Kiev, and tomorrow at 6am, I have another one.
"Then I will go back to Donetsk and from there by car to Dnepropetrovsk for another circumcision. Then I'll visit another summer camp in Dnepropetrovsk, for another five to six circumcisions. Sometimes, we make the ceremony in the hotel next to the airport, to save time. I don't always understand myself how I manage to do so many in a single day".
With wry amusement, the rabbi re-emphasises that his work is not just about babies. "Not long ago I received a call from the city of Nikolayev. There was an 82-year-old Jew who had decided that it was probably time to have his own brit milah."