The martyrs were mentioned in the presence of Abu Anaba Khawlani, and the people spoke of those who die from stomach illness, plague, and women who die in childbirth. Abu Anaba became angry and said, "The companions of our Prophet narrated to us from our Prophet ﷺ that he said, 'The martyrs of Allah on earth are Allah's trustees on earth among His creation, whether they are killed or die a natural death.'"
حدثنا أبو اليمان قال حدثنا إسماعيل بن عياش
ذكر عند أبي عنبة الخولاني الشهداء فذكروا المبطون والمطعون والنفساء فغضب أبو عنبة وقال حدثنا أصحاب نبينا عن نبينا ﷺ أنه قال إن شهداء الله في الأرض أمناء الله في الأرض في خلقه قتلوا أو ماتوا
Its isnad is hasan, because of Baqiya bin Walid, who did not state explicitly that he heard it directly. It is corroborated by the hadith, "Do you know who the martyr is?" Haythami said in 5/302, The men of Ahmad's narration are trustworthy.