2:4: “And who have faith in what is revealed to you and in what was revealed before you, and in the Hereafter they are certain”: Ibn Abbas said “They believe in what Allah sent you with, and in what the previous Messengers were sent with and they do not distinguish between (believing) them, nor do they reject what they brought from their Lord”.
“And in the Hereafter they are certain” that is the resurrection, Paradise, the Fire, the reckoning and the the Scale which measures deeds (the Mizan).
Four verses at the beginning of this Surat describe the believers, two describe the disbelievers, and thirteen describe the hypocrites. The four verses mentioned include every believer, Arab, non-Arab, or a person of a previous Scripture, whether they are Jinns or humans.
All of these attributes complement each other and require the existence of the other attributes. So whoever believes in the Unseen, also performs the prayer and gives Zakah, and believes in the previous Messengers and the Hereafter.
The People of the Book have a special significance here because when they faithfully embrace Islam, then they’ll get two rewards.
2:5: “They are on guidance from their Lord, and they are the successful”: meaning they’re following a light & have insight from Allah.
“And they are the successful” in this world and the Hereafter. They’ll have what they seek and be saved from the evil that they tried to avoid. Therefore, they will have rewards, eternal life in Paradise, and safety from the torment that Allah has prepared for His enemies.