Musnad Ahmad 1153:279

Ibn Numayr narrated to us, from Hisham, from his father, from Aisha, who said: The Messenger of Allah (peace and blessings of Allah be upon him) arrived in Medina, and it was the most pestilential of Allah’s lands. Abu Bakr fell ill. She said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "O Allah, make Medina beloved to us as our love for Mecca, or even more. Make it healthy, bless for us its mudd and its sa', and transfer its fever to al-Juhfa."