Al-Matalib al-'Aliyah 189 — Water is due to water

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "The obligation of ghusl (that is, the use of water) arises only from the emission of semen (that is, the coming out of water), and there is no harm in (impurity on the garment or body) amounting to one or two dirhams."
This narration is sahih (authentic) and reliable in its chain. The first rule mentioned in it, "al-ma' min al-ma'" (water is from water), was among the rulings of the early period of Islam, which was later abrogated in the case of intercourse by mere penetration (even without ejaculation); while the matter of pardoning a small amount of impurity (the size of a dirham) holds importance among the jurists in the chapter on purification.