Musnad Ahmad 462:17

Khalaf ibn al-Walid narrated to us, he said: Ibn ‘Ayyash narrated to us, from Buhayr ibn Sa‘d, from Khalid ibn Ma‘dan, from al-Miqdam ibn Ma‘di Karib al-Kindi, from the Prophet, peace and blessings of Allah be upon him: "Indeed, Allah, the Almighty and Majestic, enjoins you regarding your mothers. Indeed, Allah enjoins you regarding your mothers. Indeed, Allah enjoins you regarding your fathers. Indeed, Allah enjoins you regarding the nearest, then the nearest."