The expression: غَافِرِ الذَّنبِ وَقَابِلِ التَّوْبِ (ghafiridh-dhanb) in verse 3: all literally means the one who puts a cover on sins (in the sense that they are no more seen or known by anyone), and: قَابِلِ التَّوْبِ (gabilit-tawb) means: He who accepts taubah or repentance. These two expressions appear separately, though the sense of both appears to be almost the same. The reason is that by saying: غَافِرِ الذَّنبِ (ghafiridh-dhanb), the purpose is to indicate that Allah Ta’ ala does already possess the standing authority and power to forgive the sin of a servant even without taubah - while forgiving those who repent is yet another attribute of Allah. (Mazhari)
The word: طَول (tawl) which follows immediately in: ذِي الطَّوْلِ (dhit-tawl) literally means vastness and being need-free. Then, it could also mean power or favor. (Mazhari)