Yahya bin Uqayl al-Makki (may Allah have mercy on him) said: I heard Abu al-Tufayl Amir bin Wathilah (may Allah be pleased with him) say: I went to Hudhayfah bin Asid (may Allah be pleased with him), and he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "When the drop of fluid falls into the womb." Then he narrated the rest of the hadith in a similar way.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3029