All the prophets of God have said their prayers with ism-e-aazam. For instance, when on the occasion of the battle of Badr the Prophet of Islam looked at the battlefield, he saw that the enemy army was very strong as compared to the army of the believers. The believers lacked in weaponry, as well as were very small in number as compared to the enemy army. On seeing this inequality, the Prophet was emotionally very disturbed. In total helplessness, he fell down in prostration before God. At that time, he uttered these words: “O God, if You destroy this group of believers, You will never be worshipped on the earth.” (Musnad Ahmad, Hadith No. 208). This dua, in respect of Prophet’s godly feelings (rabbani feelings), was a dua with ism-e-aazam, which was accepted in the full sense. With the help of God the weaker group defeated the stronger group.
The prayer with ism-e-aazam is not peculiar only to the prophets. This prayer can be granted to every servant of God. Anyone who turns to God with sublime godly feelings in all sincerity, with full faith, may be granted the blessing of the prayer with ism-e-aazam. It can be recognized that on the occasion of such prayer, a person feels that his whole existence has bathed in the divine light. At that time he starts speaking such words as he may never previously have thought of. In history, there are many servants of God who have been granted the blessings of prayer with ism-e-aazam.
Source: Discovering God