مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3927
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah bin Masood (رضي الله عنه) said: Beware of saying. So and so died as a martyr or So and so was killed as a martyr, for a man may fight to get booty, or he may fight to be remembered, or he may fight to show off. If you must bear witness that someone is a martyr, then bear witness for the group whom The Messenger of Allah (ﷺ) sent on a campaign and they were killed, and they said: O Allah, tell our Prophet (ﷺ) about us, that we have inet You and we are pleased with You and You are pleased with us.
Musnad Ahmad 3952Its isnad is da’eef because it is interrupted. ‘Abu ‘Ubaidah