A CLASSIC Jewish story: a learned rabbi and a taxi driver depart this world at the same time and arrive together at the gates of Heaven. The angel at the gate signals to the taxi driver to enter, then turns to the rabbi and sadly shakes his head. “What is this?” asks the rabbi. “I am a learned rabbi and he is only a taxi driver who, not to put too fine a point on it, drove like a lunatic.” “Exactly so,” replies the angel. “When you spoke, people slept. But when they got into his taxi, believe me, they prayed!”

That’s a way of reminding us that prayer isn’t always predictable. We never know in advance when we will feel the need to turn to God. Why then the discipline of daily prayer?

Preparing a new edition of the Jewish prayer book has made me yet more vividly aware of how powerful prayer really is. It is, said the 11th- century poet Judah Halevi, to the soul what food is to the body. Starve a body of food and it dies. Starve a soul of prayer and it atrophies and withers. And sometimes prayer is all the more powerful for being said in words not our own, words that come to us from our people’s past, hallowed by time, resonant with the tears and hopes of earlier generations, words that gave them strength and which they handed on to us to use and cherish.

I remember visiting Auschwitz, walking through the gates with their chilling inscription, “Work makes you free”, and feeling the chill winds of Hell. It was a numbing experience. There were no words you could say. It was not until I entered one of the blocks where there was nothing but an old recording of the Jewish memorial prayer for the dead that I broke down and cried. It was then that I realised that prayer makes grief articulate. It gives us the words when there are no words. It gives sacred space to the tears that otherwise would have nowhere to go.

I think back to my father, a Jew of simple faith. In his eighties he had to go through five difficult operations, each of which made him progressively weaker. The most important things he took with him to hospital were his tefillin (the leather boxes with straps worn by Jewish men during weekday morning prayer), his prayer book and a book of psalms. I used to watch him reciting psalms and see him growing stronger as he did so. He was safe in the arms of God: that was all he knew and all he needed to know. It was only when he said to us, his sons, “Pray for me” that we knew the end was near. For him, prayer was life, and life a form of prayer.

Prayer changes the world because it changes us. It opens our eyes to the sheer wonder of existence. Is there anything in the scientific literature to match Psalm 104 as a hymn of praise to the ordered complexity of the Universe? There is something in the human spirit that, however intricately it understands the laws of physics and biochemistry, wants not merely to explain but also to celebrate; not just to understand but also to sing.

Prayer teaches us to thank, to rejoice in what we have rather than be eternally driven by what we don’t yet have. Prayer is an ongoing seminar in what Daniel Goleman calls emotional intelligence. It sensitises us to the world beyond the self: the real world, not the one defined by our devices and desires.

Daily prayer works on us in ways not immediately apparent. As the sea smooths the stone, as the repeated hammer blows of the sculptor shape the marble, so prayer — repeated, cyclical, tracking the rhythms of time itself — gradually wears away the jagged edges of our character, turning it into a work of devotional art, aligning it with the moral energies of the Universe.

Prayer is not magic. It does not bend the world to our will; if anything it does the opposite. It helps us to notice the things we otherwise take for granted. It redeems our solitude. It gives us a language of aspiration, a vocabulary of ideals. And seeing things differently, we begin to act differently. The world we build tomorrow is born in the prayers we say today.

Rabbi Sir Jonathan Sacks is the Chief Rabbi of the United Hebrew Congregations of the Commonwealth