Abu al-Ajfa' al-Sulami says that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) delivered a sermon and said: "Another (thing): about those who are killed in these expeditions of yours, or who die, you say: So-and-so was martyred. Perhaps he had loaded both sides of his mount with gold or silver, seeking the world thereby, or trade. So do not say that of them; rather, say as the Messenger of Allah (peace and blessings be upon him) said: 'Whoever is killed in the path of Allah, or dies, he will go to Paradise.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12910