My favourite prayer requires a great leap of the imagination. On the holiest days of the year, Jews pray for a time when humanity will live in harmony, everyone will recognise God's greatness and loving-kindness will fill the world.

It's a fantastic vision, but for the rabbis it was absolutely logical. World peace, Maimonides explains, is the natural corollary of belief and knowledge of God. The reason is clear. Anyone who recognises that everyone is created equally will see the senselessness of initiating violence against others; for we are all children of the same God.

Optimistically, Judaism teaches that one day, everyone will understand this. This connection between belief in God and universal harmony was expressed by Isaiah who prophesied; "They shall not hurt or destroy in all my holy mountain; for the earth shall be full of the knowledge of the Lord as the waters cover the sea" (Isaiah 11:9 quoted in Maimonides, Guide for the Perplexed 3: 11).

Although, in our current state of perpetual conflict, this may seem far-fetched, there have been instances where people en masse awoke to this realisation. The most famous took place during the First World War just over a hundred years ago this week. It is described in Malcolm Brown and Shirley Seaton's outstanding book, Christmas Truce.

As the enemy soldiers crouched in trenches just a few hundred yards from one another, they listened to each other's festive celebrations, British soldiers joined in the German carol-singing and soon, they were calling out greetings to one another across the frozen, muddy fields.

Amid the friendly banter, temporary ceasefires were declared, allowing each side to clamber out of their trenches and bury their dead. In some cases, the enemy forces dug graves together and even participated in each other's funeral services.

Once the men were standing side by side in no man's land, they swapped trophies: plum puddings, cigarettes, whisky and scraps of uniform. A surprising number of Germans had worked as waiters in London's restaurants, they were happy to converse in English and reminisce about good times in Britain.

Many veterans recalled kicking around improvised footballs; playing with the very men whom they had tried to kill the day before. They wrote letters from the front to tell their families that despite the freezing, rat-infested trenches, they felt privileged to participate in these extraordinary events.

It didn't work everywhere. Occasionally, there were misunderstandings or deliberate acts of violence in which those suing for peace were shot. Nevertheless, even where these arose, and retaliation occurred, the soldiers quickly restored quiet. Across the Western Front the truces were renewed.

Both sides eventually cracked down on "fraternisation with the enemy". Even then, troops ordered to recommence hostilities were often reluctant to kill their new-found friends. They sent messages to the opposite trenches warning them to keep their heads down especially at the times when the officers' inspection would force an
offensive.

Others salved their consciences by firing into the air rather than aiming at the enemy or by ritually firing their weapons at the same time and at the same target each day, thereby demonstrating sufficient aggression to please their commanders while assuring their enemies that no harm was intended.

A young Jewish doctor, Friederich Kohn, serving as a medical officer with a Hungarian regiment described how 20 Russian soldiers emerged from their trenches waving white flags and asking for a truce. The opposing armies shared food and drink, and when the young Jew complained of shrapnel attacks on his first aid post, the Russian colonel promised that so long as he was in command, the doctor would be safe.

For the next 14 days, his first aid post was left alone until the Russian commander sent across a rocket, signalling that his unit was leaving and the doctor should be on his guard. Apparently, there were no more major attacks on the post and the doctor survived the war, only to find himself a victim of Nazi persecution.

Sometimes, in our world of brutal conflict, peaceful gestures seem remote, but Judaism teaches us to savour each instance. That is why the restful peace of Shabbat is called "a taste of the World to Come", readying us and inspiring us with a weekly day of tranquillity as a model for the future.

Even in the midst of the current terror campaign, Israeli cafes offer discounts to Jews and Arabs who sit down to share a meal, or our hospitals care for terrorists who are wounded while launching attacks and Syrians who have crossed the border to get medical help, we are reminded of humanity's capacity for overwhelming goodness.

We can indeed look forward expectantly to the day when "wickedness will fade away like smoke and God sweeps the rule of arrogance from the earth".

Gideon Sylvester is the United Synagogue's Israel Rabbi