If a liquid impurity (such as urine) falls on the ground or floor and becomes dry with no trace, the ground will be considered pure.
In his well-known book, Fiqh As-Sunnah, Sheikh Sayyed Sabiq states: “If there are impurities on the ground, it is purified by pouring water over it. This is proven by Abu Hurayrah’s hadith about the Bedouin who urinated in the mosque, where the Prophet (peace and blessings be upon him) said that all that needed to be done for purification was to pour water over it.
Abu Qulabah said: “The drying of the ground is its purification.” `A’ishah (may Allah be pleased with her) said: “The purification of the ground is its becoming dry.” (Reported by Ibn Abi Shaybah)
It stands to reason that the above ruling refers to the case where the impurity is a liquid. If the impurity is a solid, the ground will only become pure by removal of the impurity.”