(Annajm) 53 : 55
فَبِأَيِّ آلَاءِ رَبِّكَ تَتَمَارَىٰ
Then in which of your Lord’s sign you are doubting?
The Signs mentioned in the verse refer to Allah's ability, verses, miracles, and blessings. This question addresses not the Messenger, but other mankind. That means that by using the Confirming Truth Adhikr, all doubts should be cleared, and everyone should confirm, ‘I am one in a thousand believer’. See explanation 11: 17; 15: 99; and 45: 31-32.