Make a fist. That is roughly the size of your heart. It has been beating since about six weeks after you were conceived, and if you live to 80 it will beat around three billion times without a single rest day. Each minute it moves about five litres of blood, all the blood you have, round a network of vessels long enough to circle the Earth more than once.
While you read this, your immune system is checking millions of cells for signs of trouble and quietly destroying invaders you will never know about. If you cut yourself, the repair begins within seconds. The human body is not a machine you maintain. It is, in large part, a body that maintains itself.
“Truly, We created the human being in the finest form.”
Qur'an 95:4 · our rendering
Surah at-Tin opens with oaths by the fig, the olive, Mount Sinai and 'this secure city' (Mecca), places linked with prophets. It then says humans were made in the finest form (ahsan taqwim), and warns that they can fall to the lowest of the low, except those who believe and do good. Commentators read 'finest form' as covering body, mind and the capacity for goodness.
What science shows
The heart is a double pump. The right side sends blood to the lungs to pick up oxygen; the left side, with thicker walls, pushes it out round the whole body. In about 1242 the Damascus physician Ibn al-Nafis, writing a commentary on Ibn Sina's Canon of Medicine, correctly described how blood passes from the right side of the heart through the lungs to the left, rather than through invisible holes in the heart wall as ancient doctors believed. In 1628 the English physician William Harvey proved that blood circulates round the body in a loop.
The British Heart Foundation estimates that the heart beats about 100,000 times a day. Your blood carries oxygen in about 25 trillion red blood cells, each living about 120 days. To replace them, your bone marrow makes roughly 2 to 3 million new red cells every second.
Your immune system has two main layers. The innate system responds within minutes to anything that looks foreign: white blood cells called neutrophils and macrophages rush to the site and swallow invaders. The adaptive system learns. B cells make antibodies, Y-shaped proteins that lock onto a particular germ, and by shuffling their genes your body can produce billions of different antibodies, enough to recognise germs it has never met. T cells kill infected cells. After an infection, memory cells remain, sometimes for life.
Vaccines use that memory. In 1717 Lady Mary Wortley Montagu, wife of the British ambassador in Istanbul, saw Ottoman women protect children from smallpox by 'variolation', deliberately giving a mild infection, and brought the practice to England. In 1796 Edward Jenner, a Gloucestershire doctor, showed that cowpox could protect against smallpox far more safely. In 1980 the World Health Organization declared smallpox eradicated, the only human disease ever wiped out.
Healing a wound happens in overlapping stages. Within seconds, blood vessels narrow and platelets plug the gap, and a mesh of a protein called fibrin forms a clot. Over the next days white cells clear germs and debris. Then new skin cells, blood vessels and collagen fibres fill the gap, and over weeks to months the scar is remodelled and strengthened.
Your body also renews itself constantly. The outer layer of skin is replaced roughly every month; the lining of your gut every few days. Bones are slowly dissolved and rebuilt throughout life. Yet some cells, including most of the neurons in your brain and the cells of the lens of your eye, stay with you from birth.
What each faith says
Judaism
“I will give thanks unto Thee, for I am fearfully and wonderfully made; Wonderful are Thy works; and that my soul knoweth right well.”
Psalm 139:14 · JPS 1917
After using the toilet, observant Jews say a blessing called Asher Yatzar, recorded in the Talmud (Berakhot 60b). In our rendering: 'Blessed are You... who formed the human being with wisdom and created in him many openings and many hollows. It is revealed and known before Your throne of glory that if one of them were opened, or one of them blocked, it would be impossible to survive and stand before You. Blessed are You, who heals all flesh and acts wondrously.' It is a daily reminder that ordinary health is a gift.
Saving a life (pikuach nefesh) overrides almost every other commandment in Jewish law, including Shabbat. Medicine is a honoured calling: Maimonides was court physician in Cairo, and the Talmud says a person should not live in a town without a doctor (Sanhedrin 17b).
Christianity
“For as the body is one, and has many members, and all the members of the body, being many, are one body; so also is Christ.”
1 Corinthians 12:12 · WEB
Paul writes that the body is 'a temple of the Holy Spirit' (1 Corinthians 6:19), so caring for it is part of honouring God. He also uses the body as a picture of the church: many parts, one body, each needing the others, so that 'whether one member suffers, all the members suffer with it' (1 Corinthians 12:26). Christians believe that God became human in Jesus (peace be upon him), and many draw from this a special respect for the human body.
Healing was central to Jesus' ministry in the Gospels, and Christian hospitals grew from that example, from medieval monastic infirmaries to St Bartholomew's in London (founded 1123). Many Christians pray for healing and also see doctors and nurses as part of God's work.
Islam
“And when I am ill, it is He who heals me.”
Qur'an 26:80 · our rendering
The Qur'an records the words of Abraham (peace be upon him): 'It is He who created me and guides me, who gives me food and drink, and when I am ill, it is He who heals me' (26:78-80). The Prophet Muhammad (peace be upon him) said: 'God has not sent down any disease without also sending down a cure for it' (Bukhari 5678), which Muslim physicians took as encouragement to search for treatments.
He also said: 'The believers, in their love, mercy and kindness to one another, are like one body: when one part of it aches, the rest of the body joins it in sleeplessness and fever' (Muslim 2586). Muslim medicine flourished in hospitals (bimaristans) in Baghdad, Damascus and Cairo; Ibn Sina's Canon of Medicine was a standard textbook in European universities for centuries.
Same and different
All three faiths see the body as a gift to be cared for, see healing as coming from God, and honour medicine as a holy work. Two of them, Christianity and Islam, independently use the body as a picture of a caring community. They differ on what the body means theologically: Christians uniquely believe that God took a human body in Jesus, while Judaism and Islam hold that God has no body at all.
A moment to reflect
- Your body is repairing and renewing itself right now without being asked. How does that make you feel about it?
- The hadith compares a community to a body that shares its pain. What would it look like if our street worked like that?
- Lady Mary Wortley Montagu learned a life-saving idea from Ottoman women. What might we learn from neighbours who are different from us?
- What does it mean to treat your body as a gift rather than a possession?
Watch
TED-Ed shows how the heart actually pumps blood, in four and a half minutes.
Kurzgesagt's famous animation of the immune system fighting a bacterial infection.
TED-Ed walks through how a wound heals itself.
Smarter Every Day on the change your heart made the moment you were born.
Do it together
Find your pulse at the wrist and count beats for 15 seconds, then multiply by four. Do it again after a minute of star jumps. Work out how many times your heart has beaten since you woke up.
Organise a group visit to an NHS Blood and Transplant session with neighbours from different faiths. All three traditions honour saving a life; one donation can help up to three people.
Write cards or hold a small event to thank local NHS staff, carers or first-aiders. Read the Asher Yatzar blessing, 1 Corinthians 12 and the 'one body' hadith, and talk about healing as shared work.
Go deeper
- How your heart works (British Heart Foundation) · article
- Immune system (NHS Inform / British Society for Immunology) · article
- Smallpox eradication (World Health Organization) · article
- Ibn al-Nafis and the pulmonary circulation (Britannica) · article
- Surah at-Tin 95 (Quran.com) · scripture
- Berakhot 60b, Asher Yatzar (Sefaria) · scripture
Sources (9)
- Heart beats about 100,000 times a day; pumps about 5 litres a minute: British Heart Foundation
- Ibn al-Nafis described pulmonary circulation (13th century): Britannica, Ibn al-Nafis
- Harvey demonstrated circulation in 1628: Britannica, William Harvey
- About 25 trillion red blood cells; lifespan about 120 days; millions made per second: Sender et al., PLoS Biology (2016); Britannica, red blood cell
- Innate and adaptive immunity; antibody diversity: British Society for Immunology, Bitesized Immunology
- Lady Mary Wortley Montagu brought variolation from Istanbul (1717-1721): Britannica, Lady Mary Wortley Montagu
- Jenner's cowpox vaccination (1796); smallpox eradicated 1980: World Health Organization, Smallpox
- Stages of wound healing: NCBI StatPearls, Wound healing phases
- Blood vessels long enough to circle the Earth (often quoted as about 100,000 km): British Heart Foundation, heart facts
