Saʿd ibn Abi Waqqas, one of the ten promised Paradise, was “the first of the Arabs to shoot an arrow in the cause of Allah” (al-Bukhari 3728); at Uhud the Prophet ﷺ told him: “Shoot, may my father and mother be your ransom!” (al-Bukhari 4055). When Saʿd ibn Muʿadh, chief of the Aws, died, the Prophet ﷺ said: “The Throne shook at the death of Saʿd ibn Muʿadh” (al-Bukhari 3803).
Saʿd is the very noun of the root s-ʿ-d: it means “happiness, good fortune, good omen”, and lexicographers contrast it with nahs, “ill luck”. It is one of the oldest Arabic names; it should not be confused with Saʿid, “happy”, or with Masʿud, “fortunate”, from the same family. The Quran uses the root for the blessed: “As for those who are made happy, they will be in Paradise” (11:108).
And as for those who were [destined to be] prosperous, they will be in Paradise, abiding therein as long as the heavens and the earth endure, except what your Lord should will - a bestowal uninterrupted.