It is one of the five pillars of Islam, and when you receive your personal summons from on high (the "invitation", as we call it, euphemistically), it cannot lightly be refused. So, each year, more than two million of us, prince and pauper, black and white, cast off our trappings and join as absolute equals in a physically gruelling and emotionally demanding Haj, or pilgrimage, to Mecca and the Holy Places. All must be identically clad, follow - on foot, in the heat and dust - a single prescribed route, and perform identical rituals.
The Haj is probably the largest periodic religious gathering in human history. My "call" came a few months ago. That is why I - Western educated, a former Fellow of Selwyn College Cambridge and an Islamic scholar who was recently and unexpectedly appointed Pakistani High Commissioner in London - temporarily set aside my Cambridge blazer and my diplomatic privileges last month. Clad only in two unstitched white cotton sheets, I joined the great tidal wave of humanity which sweeps across Saudi Arabia amid scenes of religious fervour that are almost beyond belief.
For a week I travelled rough with my wife, Zeenat, and our 10-year-old daughter, Nafees, as the faithful have done for over 13 centuries. Sometimes we slept under the ink-black desert sky and bright, bright stars, surrounded by hundreds of thousands of fellow believers. Not once did we encounter violence or cruelty, still less attempts at theft. Instead my abiding memory is of complete strangers saying "Brother, have you got enough to eat?" Or "Brother, are you lost? I will guide you."
Yet many Westerners see the Haj as a fundamentalist festival; alien and frightening. Next to nothing has been written by Muslims which would describe to Westerners what it is really like to go on the mass pilgrimage to Mecca. As someone who has devoted his life to explaining Islam to the West and vice versa, I feel it my duty to try to do so.
So it was that we arrived at Jeddah airport in a plane containing many British Muslims. The only concession which the Saudis made to my diplomatic status was that a protocol officer met us, swept us through the seas of white-clad pilgrims to the VIP lounge, and then escorted us to our hotel where we changed into our pilgrims' sheets. From then on we had no bodyguard, and no escort. No deference was paid to rank or privilege. Instead, we were part of a party of perhaps 40 organised by a number of successful Saudi businessmen and their wives, who had initially invited me to their country to give two lectures on the faith.
Their lives revolved around air- conditioned limousines, executive jets and servants by the score. Now, clad in their cotton sheets they had to fend for themselves - and their guests - pushing their way on to jam-packed coaches and shuffling along dusty pilgrimage routes. Saudi Arabia is a society in which women are usually segregated from men and taught to be submissive, but on the Haj this breaks down. The Saudi women were an integral part of our party, and became steadily more assertive as we discussed theological points - and when we negotiated the mechanics of our journey.
For me the most serene occasion was the night we all spent resting on the rocky soil close by Arafat, the spot where the Prophet gave his final address, stressing the oneness of Islam and that there would be no more black and white, no more Arab and non-Arab. As I looked around and saw Africans and Asians and an unexpectedly large scattering of blond, blue-eyed Americans, I understood the contemporary relevance of his message. We were an endless sea of over one million strangers who were not strangers, but brothers and sisters, all of us looking up at the stars and meditating.
It was a pleasantly warm night and a cool breeze blew. There was a constant murmuring of prayers. Water carriers, sweepers and cleaners hovered, but there were no police, no marshals, no signs of authority - and no trouble. None of the hysteria and wild disorder which so often mar great religious occasions in Pakistan, Bangladesh or India. I had intended to pray for this and that favour for friends and family, but I could not bring myself to do anything so trivial and selfish. Instead I prayed for humanity, my long-suffering country - and for peace with honour with India. For myself I asked only for strength to play my designated part in the cleansing of our nation.
Although emotionally intense, the Haj is not dour. Perhaps the most enjoyable morning was the one my wife and I spent with our vivacious young daughter at the ceremony known as stoning the three pillars. As you cast your 21 pebbles you are symbolically rejecting the devil and all his works. Because the whole ceremony was so arduous I wanted to throw the stones on Nafees's behalf, as Islam allows. But influenced by the newly found assertiveness of the Saudi women around her, she rebelled, collected her stones and we joined a dusty march 100,000 strong.
I was terrified, for the way was so narrow that people had been crushed to death here every year. My beloved daughter looked so small and so vulnerable. But she fought her way through the crowd like a little tiger to cast her stones.
Nafees showed the same determination when we came to Mecca. The injunction is that you must throw yourself into the slow- moving stream of humanity circling endlessly round the Kaabah - the sacred black structure containing the stone which stands in the centre of the Great Mosque. Each of us must make the circuit seven times in the heat. It is an endurance test, especially for children, because there is always a desperate struggle to reach out and touch the magnificent embroidered cloth which covers the stone. A youngster could be crushed to death.
No wonder I reminded Nafees that she could appoint me to make the seven circuits for her. She refused - and I was equally adamant that I dare not allow her to attempt this final ceremony with me. I asked in despair "Oh God, What should we do?" I was given my answer. We noticed stairs leading to the first floor balcony which runs round the square. And there on the balcony was a wheelchair, which appeared like a miracle. With some difficulty I persuaded Nafees to sit in it and solemnly wheeled her through the multitude.
As soon as we had finished, I had a feeling of duty done, of serenity acquired - and a new sense of perspective which is with me still. So too is the supportive knowledge that I am truly part of a vibrant worldwide community of believers.
The writer is Pakistan's High Commissioner in LondonReuse content