Musnad Ahmad 1302:40

Sufyan ibn 'Uyaynah narrated to us, from 'Ata'—meaning Ibn al-Sa'ib—from Abu 'Abd al-Rahman al-Muqri', who said: Abu al-Darda' said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "The father is the middle of the gates of Paradise, so preserve that gate or leave it."