It is reported from Anas b. Sīrīn that he said:

It once reached us in Kūfā that Masrūq used to flee from the plague. Muḥammad denied this and said, “Let us go to his wife and ask her.” So we entered upon her and asked her about this, and she replied, “No, by Allāh, he never used to flee, but he would say, ‘These are days of preoccupation, so I like to be alone during them to worship.’ So he used to go aside and be alone to do worship. Sometimes, I would sit behind him and cry because of what I saw him doing to himself; he would pray so much that his feet would swell. I heard him say, ‘the plague, abdominal disease, postpartum bleeding and drowning: whoever dies during any of them will have it in his credit as martyrdom.'”

Ibn Saʿd, Al-Ṭabaqāt Al-Kubrā 8:202 (Al-Khānji)