Short answer
In the Hanafi school a prayer breaks if you talk, eat or drink, laugh out loud, turn your chest away from the qibla, make a lot of movement unrelated to the prayer, lose your wudu, or leave out one of its fard parts. Small movements, a smile, or quickly silencing a phone do not break it.
Things that invalidate prayer include speech of any amount, even by mistake, eating and drinking, excessive movement ('amal kathir), turning the chest from the qibla, anything that breaks wudu, a quarter of a part of the awrah being uncovered for the length of a pillar, and missing a fard act. Laughing aloud breaks the prayer, and in an adult's prayer with ruku and sajdah it breaks the wudu too.
Other madhhabs
- Shafi'i
- A few words said by mistake or in ignorance do not break the prayer, reading from a mushaf is allowed, and excessive movement means about three consecutive movements.
- Maliki
- A little speech by mistake does not break the prayer and is repaired with sajdah al-sahw.
- Hanbali
- Reading from a mushaf is allowed in voluntary prayer, and laughing aloud breaks the prayer but not the wudu.
Explanation
Salah begins with the takbir and ends with the salam, and between them ordinary life is suspended. The Prophet ﷺ said nothing of people's ordinary speech is fit for the prayer. Some faults break the prayer completely, some are repaired with sajdah al-sahw, and some only make it disliked.
What breaks the prayer in the Hanafi school:
- Talking, even a word, even by mistake, including replying to a salam or saying "yarhamukallah" to someone who sneezes.
- Eating or drinking, even a little.
- Much movement: anything that would make an onlooker think you are not praying, such as using both hands to fix clothes repeatedly.
- Turning your chest away from the qibla.
- Losing wudu, such as passing wind.
- Laughing aloud. A smile does not break it.
- Crying or groaning from pain or worldly grief so that words or letters come out. Crying from fear of Allah does not break it.
- Uncovering the awrah beyond a quarter of a part, for the length of a pillar.
- Reading the Quran from a mushaf or screen, according to Abu Hanifa.
What does not break it: a glance, a small movement, scratching once or twice, coughing or clearing the throat for a need, and silencing a phone with one quick movement. Glancing at a screen without reading it aloud does not break it, but it is disliked.
The required parts are in the conditions and fard acts, and recitation slips in mistakes in recitation.
The evidence
Sahih Muslim 537
Sahih... إن هذه الصلاة لا يصلح فيها شيء من كلام الناس ...
"Nothing of people's ordinary speech is fit for this prayer."
Talking breaks the prayer.
Sunan Abi Dawud 61
Grading to be checked... مفتاح الصلاة الطهور وتحريمها التكبير وتحليلها التسليم ...
"The key to prayer is purification; its start is the takbir and its end is the salam."
Between takbir and salam, outside acts are forbidden.
Where the ruling is recorded
- Nur al-Idah with Maraqi al-Falah, Chapter on what invalidates prayer. Lists speech, eating, excessive movement, turning from the qibla and the rest.
- al-Hidaya, Kitab al-Salah, chapter on what invalidates prayer and what is disliked in it. Speech breaks prayer whether deliberate or by mistake; reading from a mushaf breaks it according to Abu Hanifa.
- al-Majmu' (Nawawi), Chapter on what invalidates prayer. The Shafi'i view on a few words said by mistake and on reading from a mushaf.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.