Sahih Ibn Khuzaymah

And the explanation of the evidence that the command of the Prophet Muhammad (peace be upon him) to wash the vessel in which a dog puts its mouth is for the purification and cleanliness of the vessel, and not, as some scholars have claimed, that the command to wash the vessel is a purely devotional act and that the vessel is pure, and that performing ablution and bathing with that water is permissible, and that drinking that water is absolutely permissible.

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Prophet Muhammad, peace and blessings be upon him, said: "When a dog puts its mouth into the utensil of any one of you, its purification is that it should be washed seven times. The first time with soil. (It should be cleaned)." In the narration of Duraqi it is « اولھا بتراب » and in the narration of Qat'i it is « اولھا بالتراب »." The first time with soil." (Both have the same meaning.)

Abu Hurairah (may Allah be pleased with him) narrates from the Prophet (peace be upon him) that: "If a dog drinks from the vessel of any one of you, then its purification and cleanliness is that he should wash it seven times."

Abu Huraira (may Allah be pleased with him) narrates that Abu al-Qasim (peace be upon him) said: "When a dog drinks from a vessel, its purification is that it should be washed seven times, the first time with soil (cleaned with earth)."