I say, with Allah's guidance: It is the urine of animals whose meat is permissible to eat, both domestic and wild, such as sheep, gazelle, and horse, and the droppings of birds whose meat is not permissible to eat, such as falcons and kites; due to necessity. It is considered light because of the conflicting texts regarding its impurity and purity, and it is preferable to consider it impure due to the presence of a preponderant factor, like the urine of animals whose meat is permissible to eat.

For the Prophet (peace be upon him) said: 'Avoid urine,' as recorded in Sunan al-Daraqutni 1:127, and he said: the preserved narration is mursal, indicating its impurity. And the narration of the people of Uraynah, where 'some people from Uraynah came to the Messenger of Allah (peace be upon him) in Medina and found it unsuitable, so the Messenger of Allah (peace be upon him) said to them: If you wish, go out to the camels of charity and drink from their milk and urine, so they did and recovered, then they attacked the shepherds, killed them, apostatized from Islam, and drove away the camels of the Messenger of Allah (peace be upon him). This reached the Prophet (peace be upon him), so he sent after them, and they were brought back, and he cut off their hands and feet, gouged out their eyes, and left them in the desert until they died,' as recorded in Sahih al-Bukhari 6:2495 and Sahih Muslim 3:1296, indicating its purity, thus the ruling was lightened due to the conflict. Similarly, the urine of the horse has conflicting texts regarding its dislike if its meat is considered disliked due to its nobility, making its urine lightened. It is called light considering the abundance of what is excused from it, not in the manner of its purification, as it does not differ in thickness and lightness. The considered amount in light impurity is a quarter of the garment or body, anything less is excused because the estimation is with the excessive amount, and a quarter has the ruling of the whole in judgments. See: Tabyin al-Haqa'iq 1:74-75, and al-Maraqi p.156, and Allah knows best.