Ali ibn Al-Hakam narrated from Al-Husayn ibn Abi Al-Ala. He said:
I asked Abu Abdullah عليه السلام about madhy (pre-seminal fluid) that touches clothing. Imam عليه السلام said: "There is no harm in it." When we repeated the question to him, Imam عليه السلام said: "Sprinkle it with water."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 269