Musnad Ahmad 1301:29

'Abd al-Razzaq narrated to us, he said: Sufyan informed us, from 'Ata' ibn al-Sa'ib, from Abu 'Abd al-Rahman al-Sulami, who said: There was a man among us whose mother did not cease urging him to marry until he married. Then she ordered him to divorce her. So he traveled to Abu al-Darda' in the Levant and said: "My mother did not cease urging me until I married, then she ordered me to divorce her." He said: "I am not one who would order you to divorce her, nor am I one who would order you to keep her. I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'The parent is the middle gate of Paradise.' So lose that gate, or preserve it." He said: So he returned, and he had already divorced her.