The Jewish principle of saving a life, pikuach nefesh, is considered to override all other commandments of the Torah. For Andrew Deaner and Jonathan Tobin, the opportunity to perform the mitzvah came amid remarkable and unexpected scenes at White Hart Lane football stadium.
As Bolton Wanderers' club doctor, Dr Tobin was one of the first on the scene when midfielder Fabrice Muamba collapsed from a cardiac arrest during the FA Cup quarter-final with Tottenham Hotspur last Saturday evening.
Dr Tobin was soon aided by Dr Deaner, a leading cardiologist and Spurs season ticket-holder, who had been watching the match from the stands with his brother, and ran on to help the battle to save the England under-21 player's life.
Dr Deaner, a Mill Hill Synagogue member, said: "Something sort of told me I should go down [on to the pitch]. The adrenaline starts pumping when you see a cardiac arrest."
Medical staff administered CPR and used a defibrillator on Mr Muamba, 23, as stunned fans looked on. In total, 15 shocks were administered before his heart started beating again. Dr Tobin said that for the 80 minutes medical staff worked to restart his heart, Mr Muamba was "in effect…dead in that time."
The Congo-born footballer was rushed to the London Chest Hospital where Dr Deaner works. Both doctors helped provide round-the-clock care as Mr Muamba continued his remarkable recovery.
Dr Tobin described how he ran onto the pitch: "I can't begin to explain the pressure. My focus was entirely on Fabrice, I didn't know players had gathered around." He said it had been extraordinary to administer mouth-to-mouth in front of 35,000 people: "This is Fabrice, not someone who has gone down in the street. It's someone I consider a friend. I know his family. There was that connection. I was thinking, 'Oh my God, it's Fabrice'.
"I had a paramedic holding my hips so I could stand and give CPR in the ambulance. I still had my football boots on."
Dr Tobin described the 24 hours after Saturday night as "the most awful time of worrying and wondering what might happen". He stayed at the hospital alongside Mr Muamba's fiancée, Shauna, and Bolton manager and chairman Owen Coyle and Phil Gartside.
"Shauna needed a positive and upbeat atmosphere and Owen and Phil helped with that. It was difficult, but absolutely heart-warming how people pulled together," he said.
"Fabrice's recovery so far has exceeded all our hopes and expectations. It's going to be a long road for him, and we cannot get carried away.
"He has one of the most extraordinary smiles you have ever seen. He's always positive and cheerful and incredibly good at bringing the best out of other people. Fabrice breaks the mould of what people think is a typical footballer. He's a very articulate young man."
Enfield-born Dr Tobin is himself a Spurs fan. He worked as a GP before joining Bolton in 2008.
That the incident happened at the ground where he watched football as a boy, and that another Jewish doctor had come to help, was surreal, he said.
"I've got to know Andrew over the last few days and I just don't have enough superlatives to describe him and his team," said Dr Tobin.
Dr Deaner, a regular volunteer at Redbridge Jewish Community Centre in his youth, said he had shared a joke with Mr Muamba as he recovered this week: "I said, 'I understand you're a very good footballer', and he said 'I try'.
"If you're going to use the term miraculous, I guess it could be used here. If you were going to make a film to teach people how to run a complex arrest, this would have been the arrest to film because everything went as it should. One thing after another just went right."
Dr Deaner, a Redbridge-born father-of-three, is a consultant cardiologist at a number of private and NHS hospitals in London. He treats patients with conditions including angina and heart disease, and carries out angioplasty and pacemaker procedures.
In 2007 he embarked on a 1,000-mile cycle ride visiting every Premier League ground in the country, with West Ham chef Keith Ross, whose life he had saved the previous year. The ride raised funds for the London Chest Hospital's stem-cell research.