Musannaf Ibn Abi Shayba 1:899

899. Abd al-A’la narrated to us, from Ma’mar, from al-Zuhri, from Talha ibn Abd Allah ibn ‘Awf, from Abu Hurayrah, that he used to say regarding janabah (major ritual impurity) on a garment: If you see its trace, wash it. If you know that it has touched it, but then it became hidden from you, wash the garment. If you are in doubt and do not know whether it touched the garment or not, then sprinkle it with water.