Whoever is killed or dies in the way of Allah is in Paradise

It is narrated from Abu al-Ajfa' al-Sulami that he said: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) addressed us in a sermon and said: "Beware! Do not go to excess in the dowries of women (do not fix very high dowries), for if this were a mark of nobility or honour in this world, or a sign of piety with Allah, then Muhammad (peace and blessings be upon him) would have been more deserving and more fitting for it than all of you; yet he (peace and blessings be upon him) did not fix the dowry of any of his wives at more than twelve uqiyah. And indeed a man makes his wife's dowry so (excessively) costly that enmity towards her arises in his heart, and he begins to say (to himself): 'For your sake I have borne the burden, straining even the strap of the waterskin (that is, with great toil and hardship).'" (Sayyiduna Umar (may Allah be pleased with him) further said:) "And another thing you say about those killed in these battles of yours: 'So-and-so was killed a martyr,' or 'So-and-so died a martyr,' while perhaps he had loaded the hindquarters of his animal or the saddle of his mount with gold and silver in pursuit of the world. So do not say that; rather say what the Messenger of Allah (peace and blessings be upon him) said: 'Whoever is killed or dies in the path of Allah, he is in Paradise.'"
The chain of this hadith is sahih (authentic), but the two Shaykhs (Bukhari and Muslim) did not record it. Ayyub al-Sakhtiyani, Habib bin al-Shahid, Hisham bin Hassan, Salamah bin Alqamah, Mansur bin Zadhan, Awf bin Abi Jamilah and Yahya bin Atiq all transmitted it from Muhammad bin Sirin with sahih narrations. The name of Abu al-Ajfa' al-Sulami is Harim bin Hayyan, and he is among the trustworthy (thiqah) narrators.

Abbas bin Muhammad al-Duri narrates that he heard Yahya bin Ma'in say that Abd al-Rahman bin Mahdi said: The name of Abu al-Ajfa' is Harim. This hadith has also been transmitted by Salim bin Abdullah and Nafi' from Sayyiduna Ibn Umar (may Allah be pleased with them both) as a sound (mustaqim) narration.