Musnad Ahmad 32:217

Yahya ibn Sa'id narrated to us, Hammad ibn Zayd narrated to us, 'Ubayd Allah ibn Abi Bakr narrated to us, from Anas, from the Prophet, peace and blessings of Allah be upon him, who said: "Indeed, Allah has appointed an angel over the womb. He says: 'O Lord, a drop (nutfa). O Lord, a clot ('alaqa). O Lord, a lump of flesh (mudgha).' So when the Lord decrees its creation, he says: 'O Lord, is it wretched or happy? Is it male or female? And what is the provision and what is the lifespan?' He said: 'So it is written like that in the womb of its mother.'"