Firstly: Defining Residues
Residues linguistically: As'ar is the plural of Su'r, and it refers to excess and surplus.
Residues technically: what remains in a vessel and its like of food and drink.
Secondly: Rulings Pertaining to Residues
1. The purity of human residues
The food and drink residues of a human being are pure, regardless of whether they were Muslim or disbelieving, and in a state of janabah  Major impurity requiring ritual washing to remove, caused by intercourse or ejaculation. Janabah is the state, and junub is the one who is in that state. or menses. This is by agreement of the four schools of jurisprudence.  The Hanafis excluded two scenarios: 1) Residues of one who drinks alcohol; 2) One whose mouth bleeds if he drinks immediately, and his mouth is pure if he continuously swallows. It is also the position of the Zahiris and the juristic verdict generally.
2. The purity of the residues of creatures whose flesh is eaten
The residues of animals who are consumed by humans are pure. Consensus has been quoted over this matter by Ibn al-Mundhir, Ibn Hazm, and Ibn Rushd.
3. The purity of cats’ residues
The residues of cats are pure, and this is the position of the majority of Malikis, Shafi`is, and Hanbalis. Abu Yusuf holds this position from among the Hanafis, and it is the most common position among scholars.
4. The purity of residue from mules and domesticated donkeys
The residues of mules and domesticated donkeys are pure. This is the position of the Malikis, Shafi`is, a narration from Ahmad, a group from the Salaf, and it is the choice of Ibn Qudamah, Ibn Baz, and Ibn `Uthaymin.
5. The purity of the residues of creatures that do not keep away from najasah generally
The residues of animals that do not keep away from najasah normally are makruh  Makruh is one of the five Islamic legal rulings, and it means that the matter in question is prohibited but not sinful if committed, so legally disliked. according to the Hanafis, Malikis, and Hanbalis, like mice and untamed chickens.
6. The purity of the residues of carnivorous land animals  Except dogs and pigs. and birds of prey
Residues from carnivorous land animals like wolves, tigers, and lions, and birds of prey like falcons, are all pure. This is the position of Malik, al-Shafi`i, a narration from Ahmad, the choice of Ibn al-Mundhir, Ibn Hazm, and Ibn `Uthaymin, and in its accordance is the Permanent Committee's verdict.
7. The ruling of residue from dogs and pigs
Residues from dogs and pigs are impure according to the majority: Hanafis, Shafi`is, and Hanbalis, and Ibn Rushd the grandson  Latinised Averros (d. 595 AH). Nicknamed so to distinguish him from his grandfather, also Ibn Rushd al-Maliki (d. 520 AH). leant towards this opinion among Malikis.