IT ISN’T easy watching a parent die. My late father underwent five big operations in his eighties. Each time he grew weaker and feared that this trial would be his last. He didn’t talk about it, but we, his children, could see it in his eyes.

He was a proud man, proud of his strength — he was physically tougher than any of us — and of his independence. He hated being a burden on anyone. It would have been so easy for him to say, honestly, convincingly: “I want to end it now.” Luckily he was spared that choice. Assisted dying was not on the public agenda then. Had it been, and had he availed himself of it, we would never have known whose pain he was seeking to avoid: his or ours.

Towards the end, we took turns to sit by his bedside. One Sabbath morning, my brother Alan was sitting next to him, saying the morning prayers. He reached the passage in which we say: “My God, the soul you gave me is pure. You breathed it into me, You guard it while it is within me and one day You will take it from me.” At that point, my father died. Coincidence? I don’t know. All I know is that it made sense to us. For he was a man who, despite his independence and pride, knew that there are some things you leave to God. God gave us life. God will decide when to take it back.

The Bill to legalise assisted dying comes before Parliament this coming week. The Jewish tradition, going back many centuries, is strongly opposed to such acts. Life is sacred. It is God’s gift, not ours. It is the physician’s responsibility to heal, not harm, even if the patient requests it. Despite Judaism’s strong emphasis on human choice, free will and personal responsibility, we believe there are certain things we may not do, even out of great compassion.

What do we mean when we say that “life is sacred”? Sadly, the words we need to explain it have largely gone out of circulation: words such as humility, reverence, awe. Today humility is a forgotten virtue. Reverence is in short supply. Awe is not as awesome as it once was.

Perhaps the easiest way of explaining it is that things that are sacrosanct are not ours to do with as we wish. The environment is one. Personal dignity is another. Human life is a third. The wisdom of the ages has taught us not to regard these things as if they were our personal possessions. Why?

The self-professed agnostic Friedrich Hayek explained it best in his last book The Fatal Conceit. He pointed out that human intervention in history has often been catastrophic. Yet those who came before us were not foolish. How did they make what seem in retrospect to be disastrous decisions? Hayek’s answer was the law of unintended consequences, which says that whatever you foresee as the result of your choice is only a small part of the story. Decisions have ripples of consequence no one can predict at the time. Our knowledge of the future is unlike our knowledge of the past. We can see clearly in hindsight. But in the case of the future we can hardly see more than a few feet in front of our eyes.

Hayek held that the simplest way of avoiding catastrophe is to keep to a few simple rules — rules that have proved their worth by ensuring the survival of cultures that kept them. By far the longest-lived cultures are the great world faiths, and their rules are often in the form of basic prohibitions: “Thou shalt not . . . ”

To legalise assisted dying is fraught with dangers, chief of which is the deconsecration of life. The history of societies that have sanctioned euthanasia in the past is not an encouraging one. In part, Judaism and Christianity were protests against ages in which human life was held dispensable and disposable.

Those who propose the current Bill do so from the highest of motives. But purity of motive has never ensured rightness of outcomes; often it has been the reverse. To give the dying dignity, using all possible means to treat their pain is one thing. To allow medically assisted suicide is another. If we lose our reverence for human life we will one day lose much else besides.

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