He is one of the Asharah Mubasharah – the ten Sahabah y who were given the glad tidings of Jannah in this world. He accepted Islam in its early stages at the age of seventeen. He participated in every battle with Rasulullah (Sallallahu Alaihi Wasallam) and was the first to fire an arrow in Islam. He was the last of the Asharah Mubasharah to pass away in 55/56 AH - at the age of 88.
Hazrat Ali (R) narrates, “I did not hear Rasulullah (Sallallahu Alaihi Wasallam) say, 'May my parents be sacrificed for you' for anyone except Sa'd bin Malik (Abi Waqqas). I heard Rasulullah (Sallallahu Alaihi Wasallam) say to him in the Battle of Uhud, 'O Sa'd! Keep firing arrows. May my parents be sacrificed for you'.” (Bukhari, Muslim)
The same was said to Hazrat Zubair (R)
Hazrat Sa'd (R) was also a person whose duas were readily accepted. This was on account of the dua Rasulullah (Sallallahu Alaihi Wasallam) made for him: “O Allah! Allow his arrows to strike the target and accept his duas.” (Mustadrak Hakim)