Short answer
Because it is the sunnah. The Prophet ﷺ broke his fast with fresh dates, or dried dates if there were none, or a few sips of water if there were no dates. It is recommended, not required: you can break your fast with any halal food or drink.
Breaking the fast with dates, and otherwise with water, is mustahabb (recommended). Breaking it with anything else that is halal is permissible with no dislike.
The four schools agree on this.
Explanation
Anas ibn Malik described the iftar of the Prophet ﷺ: he broke his fast on a few fresh dates before he prayed; if there were none, on dried dates; and if there were none, he took a few sips of water. Muslims follow this to earn the reward of the sunnah.
The order of preference:
- Fresh dates (rutab).
- Dried dates (tamr).
- Water.
- Then anything halal.
Can I break my fast with something else? Yes. Coffee, juice, lemon water, soup, a sweet or a full meal all end the fast. The fast is over at sunset whatever you eat or drink. Choosing dates or water simply adds the reward of following the sunnah.
Is there a hadith giving the reason? A hadith in Sunan al-Tirmidhi says to break the fast with dates because they are a blessing, and with water because it purifies. Al-Tirmidhi graded it sound, but other hadith scholars judged its chain weak, so it is not relied on as proof, though its meaning is good. Dates are also an easy source of quick energy after a long day without food. But Muslims start with dates because the Prophet ﷺ did.
After the first bite, say the iftar dua and pray Maghrib. See iftar before Maghrib and the dua for breaking the fast. The four schools agree that dates, then water, are recommended.
The evidence
Sunan Abi Dawud 2356
Grading to be checked... يفطر على رطبات قبل أن يصلي فإن لم تكن رطبات فعلى تمرات ...
"He would break his fast on fresh dates before praying; if there were none, then on dried dates."
Dates, then water, are the sunnah of iftar.
Sunan Abi Dawud 2357
Grading to be checked... ذهب الظمأ وابتلت العروق وثبت الأجر إن شاء الله ...
"The thirst has gone, the veins are moistened, and the reward is certain, if Allah wills."
The dua the Prophet ﷺ said when breaking his fast.
Where the ruling is recorded
- Nur al-Idah with Maraqi al-Falah, Kitab al-Sawm, chapter on what is recommended for the fasting person. It is recommended to break the fast with dates, and otherwise with water.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Sawm, chapter on what is disliked and recommended for the fasting person. Breaking the fast with something sweet such as dates is recommended.
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.