I say, and with God's success: Stagnant water can be either little or much: First: Little stagnant water: This is water whose area is less than ten arms by ten arms — which equals (25) square meters of water surface area, and a depth from which the ground cannot be seen by scooping from it — and the ruling on little water if it is stagnant is that it becomes impure if impurity falls into it, if it is known with certainty or with a preponderance of suspicion, even if the effect of the impurity does not appear in it; as narrated by Al-Bukhari from Abu Huraira (may Allah be pleased with him): "None of you should urinate in stagnant water that does not flow, then wash in it." Second: Much stagnant water: This is water that does not move one side when the other side moves, and scholars have defined it by area, estimating it at ten arms by ten arms — which equals (25) square meters of water surface area, and a depth from which the ground cannot be seen by scooping from it — and the ruling on much water if it is stagnant is that it does not become impure unless the effect of impurity is seen in it by changing its taste, color, or smell, even at the point of occurrence, even if the impurity has a substance, such as if it is visible and apparent, one should not perform ablution from its place; and the evidence for estimating much water as being ten by ten is that the essence of the matter is that a large pond that does not move one of its sides when the other side is moved, if impurity falls into one of its sides, it is permissible to perform ablution on the other side, and this was estimated at ten by ten. It was estimated based on what was narrated from the hadith of Abu Huraira and Abdullah ibn Mughaffal (may Allah be pleased with them), where he (peace be upon him) said: "Whoever digs a well, he has a surrounding area of forty arms around it," in Sunan Ibn Majah 2: 831, Musnad Ahmad 2: 494, Sunan al-Daraqutni 4: 220, and the verification in the hadiths of disagreement 2: 225, and Al-Zailai has covered its paths in Nasb al-Rayah 4: 291-292, and he refuted Al-Daraqutni's statement that the correct view is that it is interrupted. Thus, it has a sanctuary from every side of ten, so it is understood from this that if another person wants to dig a well in its sanctuary, he is prevented from doing so; because the water is attracted to it, and the water in the first well decreases. If another person wants to dig a hole to throw impurities or the like, and the drainage flows in the sanctuary of the first well, he is not allowed to do so; due to the transmission of impurity to the first well, and the pollution of its water, and he is not prevented from doing so beyond the sanctuary, which is ten by ten. Thus, it is known that the Sharia has considered the ten by ten in the non-transmission of impurity, even if the impurity transmits, it is ruled that it is prohibited. See: Umdat al-Ri'ayah 1: 88, Sharh al-Wiqayah p. 99, the glorious commentary on the Muwatta of Muhammad 1: 269-270, and Al-Sayah p. 370-385, Al-Badai 1: 72, and Al-Mabsut 1: 70-71, and Allah knows best.