Short answer
The Prophet ﷺ said that when you hear dogs barking or donkeys braying at night, seek refuge in Allah, because they see what you do not see. So the sunnah is to say A'udhu billahi min ash-shaytan ir-rajim. It is not an omen of death or bad luck.
Seeking refuge in Allah when you hear dogs barking or donkeys braying at night is sunnah. Treating the barking as an omen of death or misfortune is a forbidden superstition.
The four schools agree on this.
Explanation
Jabir reported that the Prophet ﷺ said: when you hear dogs barking and donkeys braying at night, seek refuge in Allah, for they see what you do not see. In Sahih al-Bukhari he said that when you hear a donkey bray, seek refuge in Allah from Shaytan, because it has seen a devil, and when you hear a rooster crow, ask Allah for His bounty, because it has seen an angel.
The scholars took from this that some animals can sense or see devils and jinn that humans cannot. That is a reason to remember Allah, not a reason to fear. Dogs also bark at people, cars, cats and noises, so not every bark at night is about the unseen.
What to do:
- say A'udhu billahi min ash-shaytan ir-rajim;
- if you are about to sleep, read Ayat al-Kursi and the last three surahs, as in the bedtime duas;
- carry on with your night calmly.
What it does not mean: some cultures say that a dog howling at night means someone will die, or that bad luck is coming to the house. Islam rejects omens of this kind; the Prophet ﷺ said there is no tiyarah. Good and harm come only from Allah. See superstitions in Islam.
For more on dogs and jinn, see Dogs in Islam and Jinn in Islam.
The evidence
Sunan Abi Dawud 5103
Grading to be checked... إذا سمعتم نباح الكلاب ونهيق الحمر بالليل فتعوذوا بالله فإنهن يرين ما لا ترون ...
"When you hear dogs barking and donkeys braying at night, seek refuge in Allah, for they see what you do not see."
The sunnah response to barking at night is to seek refuge.
Sahih al-Bukhari 3303
Sahih... وإذا سمعتم نهيق الحمار فتعوذوا بالله من الشيطان فإنه رأى شيطانا ...
"When you hear a donkey braying, seek refuge in Allah from Shaytan, for it has seen a devil."
Some animals see devils that people cannot.
Where the ruling is recorded
- Fath al-Bari (Ibn Hajar), Kitab Bad' al-Khalq, commentary on the hadith of the rooster and the donkey. Comments on animals seeing angels and devils.
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.