Musnad Abu Ya'la al-Mawsili 98:2

Zahmūyah narrated to us, [he said] Ibn Abī al-Zinād narrated to us, from Yaḥyā ibn Saʿīd ibn Dīnār, the freed slave of the family of al-Zubayr, [who said]: The trustworthy one informed me that the Messenger of Allah (may Allah bless him and grant him peace) forbade on the day of Khaybar having intercourse with pregnant women. And he said: "Do not irrigate the crop of someone else."