Sayyiduna Shakal bin Humayd (may Allah be pleased with him) said: I came to the Messenger of Allah (peace and blessings be upon him) and said: O Messenger of Allah! Teach me a supplication for refuge with which I may seek refuge? He (peace and blessings be upon him) took my hand and then said: "Say: 'I seek refuge in You from the evil of my soul, from the evil of my hearing, from the evil of my sight, from the evil of my tongue, from the evil of my heart, and from the evil of my semen (mani).'" Then he said to me: "Memorise it." Sa'd (may Allah have mercy on him) said: And by mani is meant his fluid.
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7194