Sayyiduna Umar bin Khattab, may Allah be pleased with him, said: When a man is killed in your battles, you say about him that so-and-so has become a martyr, whereas it is possible that he had loaded gold and silver on the back of his animal or on the sides of his mount for the sake of trade. Therefore, do not say this statement of martyrdom about anyone. Yes, you may say what Muhammad, the Messenger of Allah, peace and blessings be upon him, said: Whoever is martyred in the way of Allah will go to Paradise.
Hadith Referenceالفتح الربانی / كتاب الجهاد / 4897
Benefits: … The fundamental point is that, in light of predominant assumption (zann ghalib), every worshipper is addressed with a specific title; for example, one who performs prayer is called a “prayerful person” (namazi) and is remembered with good words, even though it is Allah Ta’ala alone who knows whether his prayer has been accepted or not, and whether his prayer has become a means of mercy for him or a cause of punishment. The same situation applies to fasting, pilgrimage (hajj), zakat, jihad, and indeed every good deed. If we call someone a “haji” (pilgrim) or “shaheed” (martyr), we are, in reality, saying so based on our good opinion or predominant assumption; the final decision rests with Allah Ta’ala alone.