Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "Fever and headache keep afflicting a male or female servant (of Allah), even though they both carry sins as great as Mount Uhud; but when these two illnesses leave him, not even the weight of a mustard seed of sin remains on them (that is, on the male or female servant)."
Abu Ya'la recorded it, and its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجنائز / 3797