Allahu a'lam, Allah knows best.

Allahu a'lam (اللَّهُ أَعْلَمُ) means "Allah knows best". A'lam means "most knowing". You say it when you are unsure, or to admit that your answer is your best understanding and Allah's knowledge is complete.

Saying "I don't know" is knowledge

Abdullah ibn Masud said: "Part of knowledge is that a person says, about what he does not know, Allah knows best" (Sahih al-Bukhari, from Ibn Masud). The great scholars were known for saying "I do not know" when asked about what they had not studied. Guessing about religion is far worse than admitting you are unsure.

The Companions' answer

When the Prophet ﷺ asked Mu'adh, "Do you know what Allah's right over His servants is?", Mu'adh replied: "Allah and His Messenger know best" (Sahih al-Bukhari 2856, Sahih Muslim 30). The Companions answered this way to many of his questions. After the Prophet's ﷺ death, scholars say only "Allahu a'lam" for matters of the unseen.

Wallahu a'lam and wallahu a'lam bis-sawab

• Wallahu a'lam (وَاللَّهُ أَعْلَمُ), "and Allah knows best", is how many fatwas and answers end.
• Wallahu a'lam bis-sawab, "and Allah knows best what is correct", is a longer form used in the same way.

AmalKit's guides are written in the same spirit: we cite our sources, and our scholars review them, but Allah knows best.

When not to use it

Allahu a'lam is honest humility, not a way out of a question. If you know something clearly, such as what the Quran plainly states, say it. And do not use "Allah knows best" to cast doubt on a clear ruling. Use it when you are truly unsure, or to close an answer you have tried your best to get right. Saying "Allah knows best" in English carries the same meaning.

Spellings

Allahu a'lam, allahu alam, Allah alam, allahu aalam and wallahu alam are all used. The apostrophe marks the Arabic letter ʿayn in aʿlam.

1. Sahih al-Bukhari, Kitab at-Tafsir, from Abdullah ibn Masud.
2. Sahih al-Bukhari 2856; Sahih Muslim 30.