Discover the meaning of the term Al-aṣl (أصل) in Islamic vocabulary.
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Updated on 11 April 2026 at 1:05 AM
📖 8 min readIt is that upon which something else is built.
In language: that upon which something else is built, in the sense that something else is established upon it, even through reflection and reference to another matter as a branch. Do you not see that the evidences of fiqh, upon which the issues of fiqh are built, are usul (roots), and that they are built upon the science of tawhid as branches? And they are built upon the science of tawhid only because reasoning by means of them depends on knowing their validity, which depends on knowing the Creator, His attributes, and prophethood, and this is the science of tawhid. Whoever defines the asl without mentioning the said condition should not be taken to have intended to exclude it; rather it is intended categorically (qat'an) in either manner, and the asl is among relational matters (al-umur al-idafiyya). The condition is indispensable in defining relational matters, though it is often omitted because of their fame. Building is inclusive of the sensory and the rational: both the wall and the evidence are an asl, the roof being built upon the wall as sensory building, and the ruling upon its evidence as rational building. It is objected, however, that building one thing upon another is a relation between the two, and relations are all intellectual, not sensory, matters as established in philosophy (al-hikma), so the division into the sensory is not sound.
In language: the lower part of a thing. In technical usage it is applied to that upon which something else is built, and is then contrasted with the branch (al-far'), or with what the preponderant (ar-rajih) rests on, or with the evidence, or with the constant rule, or with what derives from it, as the father from whom his children derive. The asl pluralizes to asul, and its use multiplied until it was employed for everything upon which something else rests and is built, in the sense that it is built upon it and derives from it: the father is the asl of the child, the foundation the asl of the wall, the river the asl of the channel, whether the building be sensory, as in the example, or rational, as the building of the signified upon the evidence. The asl is also used technically in meanings that all go back to the branch's resting on its root and its establishment and building upon it; among those technical meanings: 1. the evidence as opposed to the signified; 2. the general rule. With the jurists it is that upon which the branch is measured by means of an effective cause extracted from it. It is that upon which something else is built. The asl of any thing is its rule, such that were it imagined lifted, everything dependent on it rises with it; al-Raghib mentioned it. Al-Fayyumi said: the asl of a thing is its lower part; the foundation of a wall is its lower part; 'ista'asala the thing' means its root became fixed and strong; then usage spread until it was said: the asl of anything is what the existence of that thing rests upon: the father is the asl of the child; 'asaltuhu ta'silan' means you gave it a fixed root upon which something else is built. As for their saying 'they have no asl and no fasl', it means they have no lineage nor eloquence, or: no reason nor eloquence.
Awhama (he made believe), with fatha on the waw; then the hamza takes kasra, because some of the Arabs inflect the aorist pattern (mustaqbal fa'ila) with kasra, saying: a'lamu, ni'lamu, ti'lamu. When the hamza of 'awhamu' takes kasra, the waw changes into ya'.
The thing 'aslan': to examine it thoroughly until one knows its origin. Al-asl: the foundation of a thing upon which it stands (plural: usul): the origin of a thing from which it grows. Nobility of lineage. Their saying 'he has no asl and no fasl': al-Kisa'i said the asl is maternal lineage (hasab) and the fasl descent (nasab). The intellect: said Ibn al-A'rabi. In their saying 'I did not do it aslan' and 'I shall never do it aslan': meaning I never did it and shall never do it; it is in the accusative as an adverbial (zarfiyya), that is: I did it at no time nor on any occasion. In the Law: an expression for what something else is built upon, itself not being built upon anything; and: what whose ruling is established by itself and upon which something else is built (al-Jurjani). Al-usul (plural of asl). In technical usage: the preponderant (ar-rajih), the presumptive (al-mustasahab), the apparent (az-zahir), the evidence, the ritual element (at-ta'abbud), the predominant (al-ghalib), and the mitigating factor (al-mukhrij) (Atfaysh). In the Hanafi saying 'thus in the recension of the Usul': it means the books of Muhammad b. al-Hasan ash-Shaybani: al-Jami' as-Saghir, al-Jami' al-Kabir, al-Mabsut, az-Ziyadat, as-Sir al-Kabir, and as-Sir as-Saghir. Al-usul in the sale of roots and fruits among the Shafi'is: trees and everything that fruits time after time; or: the roots; or: the green plant itself; or: the tree and the land; or: the building and the tree. As-Subki said: that is far-fetched. Or: the land and the tree together with the fruits. As-Subki said: that is far-fetched. Among the Hanbalis: like the fourth Shafi'i view.
That upon which something else is built. The asl of any thing is its rule, such that were it imagined lifted, everything dependent on it would rise with it; al-Raghib mentioned it (al-Mufradat, root 19). Al-Fayyumi said (he is Ahmad b. Muhammad b. 'Ali al-Fayyumi, d. 770 AH; al-Fayyumi refers to Fayyum of Iraq, a place near Hayth in Iraq; see al-Misbah al-Munir, entry asl, p. 6): the asl of a thing is its lower part; the foundation of a wall is its asl; 'ista'asl the thing': its root became fixed and strong; then it spread until it came to be accepted that the asl of anything is what the existence of that thing rests upon: the father is the asl of the child, and the river the asl of the channel. 'Asaltuhu ta'silan' means you established for it a fixed root upon which something else is built. Their saying 'he has no asl and no fasl' means he has no lineage nor eloquence, or no reason nor eloquence. Al-'asil is the time from after the afternoon prayer until sunset. 'Ista'aslahu' means he uprooted it with its roots. Their saying 'ma fa'altuhu aslan' means I never did it and shall never do it, it being in the accusative as an adverbial, that is: I did it at no time nor on any occasion.
﴿أَلَمْ تَرَ كَيْفَ ضَرَبَ ٱللَّهُ مَثَلًۭا كَلِمَةًۭ طَيِّبَةًۭ كَشَجَرَةٍۢ طَيِّبَةٍ أَصْلُهَا ثَابِتٌۭ وَفَرْعُهَا فِى ٱلسَّمَآءِ﴾
« Have you not considered how Allah presents an example, [making] a good word like a good tree, whose root is firmly fixed and its branches [high] in the sky? »
Surah ابراهيم : 24
﴿ٱصْلَوْهَا ٱلْيَوْمَ بِمَا كُنتُمْ تَكْفُرُونَ﴾
« [Enter to] burn therein today for what you used to deny." »
Surah يس : 64
﴿إِنَّهَا شَجَرَةٌۭ تَخْرُجُ فِىٓ أَصْلِ ٱلْجَحِيمِ﴾
« Indeed, it is a tree issuing from the bottom of the Hellfire, »
Surah الصافات : 64
﴿ٱصْلَوْهَا فَٱصْبِرُوٓا۟ أَوْ لَا تَصْبِرُوا۟ سَوَآءٌ عَلَيْكُمْ ۖ إِنَّمَا تُجْزَوْنَ مَا كُنتُمْ تَعْمَلُونَ﴾
« [Enter to] burn therein; then be patient or impatient - it is all the same for you. You are only being recompensed [for] what you used to do." »
Surah الطور : 16