Musnad Ahmad 1153:1097

Yazid narrated to us, Sakhr ibn Juwayriyah informed us, from Isma'il, from Abu Khalaf, that he entered with 'Ubayd ibn 'Umayr upon 'Aishah. 'Ubayd ibn 'Umayr asked her: "How did the Messenger of Allah, may Allah bless him and grant him peace, recite this verse: 'Alladhina ya'tuna ma atau' (those who do what they do) or 'Alladhina yu'tuna ma atau' (those who give what they give)?" She said: "Which of the two is more beloved to you?" He said: "By Allah, one of them is more beloved to me than such and such." She said: "Which of them?" He said: "'Alladhina ya'tuna ma atau'." She said: "I bear witness that that is how the Messenger of Allah, may Allah bless him and grant him peace, used to recite it, and that is how it was revealed, but the spelling is a letter [different]."