Jami` at-Tirmidhi Book 10, Hadith 98
"I heard my grandfather, the father of my mother, Simak bin Al-Walid Al-Hanadi narrating, that he heard Ibn Abbas narrated, that he heard the Messenger of Allah saying: "Whoever has two predecessors (in death) among my Ummah, then Allah will admit them into Paradise."So Aishah said to him: "What about one from your Ummar who has one precessor?" He (pbuh) said: "And whoever has one predecessor O Muwaffaqqah!" So she said: "What about one who does not have a predecessor from your Ummah?" He said: "I am the predecessor for my Ummah: you will never suffer (in grief) for (the loss of) anyone similar to me."
The Messenger of Allah said: "Whoever has three that precede him (in death) while they did not reach the age of puberty, then they will be a well-fortified fortress for him against the Fire."
The Messenger of Allah said: "The martyrs are five: Those who die of the plague, stomach illness, drowning, being crushed, and the martyr in the cause of Allah"