The sound of singing came over the fence with such compelling harmony that I simply had to get up from my desk and follow the music. It came from the home of my colleague, friend and neighbour, Rabbi Zahavit Shalev. Seated around the fire-pit in her garden were at least ten people playing the guitar and fifty more singing along. There were parents and children, and grandparents too. There was L. who still keeps the yellow star his family had to wear in the Budapest ghetto in his Passover Haggadah. There was M. who’d never been to a Jewish occasion before. There were lots of teens and young people.

It was the night of Lag Be’Omer, the 33rd day of the Omer, so-named after the measure of grain offered in the temple on its first night. The counting of the Omer marks the seven weeks between Passover and Shavuot. It’s traditionally a period of mourning, but Lag Be’Omer is a day of respite, a date for music and joy. ‘Despite the fact that Jewish history has more than its share of bleak and depressing chapters, the tradition sees itself as a joyous one,’ writes Arthur Green on the opening page of his delightful short book, Judaism’s 10 Best Ideas. Seeking God should fill the heart with joy: ‘Love, the wonders of nature, music, dance, and the close companionship of friends are all there to keep you on the path of joy.’ (We each have our strengths: ask me to join the dance and I’ve got two left feet; suggest a fifteen mile-hike in the wild countryside and the boots are on my feet.)

Lag Be’Omer has its hero, Rabbi Shimon bar Yochai, who lived in 2nd century Palestine. Betrayed to the Roman authorities for speaking ill of them, he flees to a cave where he hides with his son for twelve years. A well of water miraculously appears at the entrance, where a carob tree provides all the nutrition they need. Each day, every day, father and son study Torah together from memory.

Eventually Elijah announces that the Caesar who wanted them killed, has himself bitten the dust. Emerging from their cave, Rabbi Shimon and his son are dismayed at the sheer ordinariness of the world: ‘What,’ they exclaim, ‘People mundanely plough and sow, forgetting higher matters!’ A voice from heaven rebukes them: ‘Have you come out to destroy my world? Get back to your cave!’

When they re-emerge a year later (a period, perhaps, to process their post-traumatic stress) Rabbi Shimon has changed. Wherever he looks, he heals. Don’t remember me in sorrow, he says on his deathbed; let the anniversary of my death be a Hillula, a date for praising God with joy. That’s why Lag Be’Omer is also known as Hillula deRashbi (short for Rabbi Shimon bar Yochai).

This story could be a parable for the whole history of the Jewish People, and other peoples, and individuals too, who’ve faced marginalisation and persecution. Don’t be daunted or diverted; deepen your own identity, seek the nourished of your spirit. Then, if and when the blessings of freedom come, don’t be disdainful of the world, don’t be bitter. Try to be a healer; bring understanding, foster conciliation. Behave in such a way that people will remember you with joy.

Judaism expresses this as the principle of simchah shel mitzvah, the joy which comes with practising God’s commandments, with doing what’s just, kind and good. ‘A mitzvah is a place where you can meet God,’ continues Arthur Green, ‘of course it makes you happy’ [his italics]. I would add that it’s also, or even more so, a place where we meet other people, our friends and companions in trying to bring happiness and healing in this challenging world.