Musnad Ahmad 482:157

'Ali ibn Ishaq narrated to us, 'Abdullah narrated to us, Ibn Lahi'ah informed us, Bakr ibn Sawadah narrated to me, that a man narrated to him from Rabi'ah ibn Qays, that he narrated to him that he heard 'Uqbah ibn 'Amir al-Juhani saying: I heard the Messenger of Allah (may Allah bless him and grant him peace) saying: "Whoever performs ablution and perfects the ablution, then prays a prayer without being heedless or distracted, whatever was before it of anything will be expiated for him."