Those who ask leave are the ones who do not acknowledge God and the Last day, and their hearts are in doubt. In their doubts they are wavering.
Translation endnotes
[9:45] Hypocrites and polytheists claim that they believe in God (23:84-90). Indeed, with their faith in the intercession of prophets and saints, they profess faith in the hereafter (10:18). Nevertheless, they have doubts in their compromised faith, which is the result of joining the bandwagon or wishful thinking (9:45; 11:110; 14:9; 34:21; 41:45; 44:9). We are told that a conviction/acknowledgement based on knowledge is not contaminated with doubts (49:15). Ironically, many polytheists are in denial of their polytheism (6:23).