No Bodily or Mental Defects
Anas says that God's Messenger was the most handsome of people. Jabir ibn Samura remarks: "Once during a full moon, we were sitting in the mosque. God's Messenger came in. I looked first at the shining moon, and then at his face. I swear by God that his face was brighter than the moon." 
Prophets must be free from all bodily defects, for their appearance should not repel others. In explaining the Divine wisdom of God's Messenger living for 63 years, Said Nursi writes:
Believers are religiously obliged to love and respect God's Messenger to the utmost degree, and follow his every command without feeling any dislike for any aspect of him. For this reason, God did not allow him to live to the troublesome and often humiliating period of old age, and sent him to the "highest abode" when he was 63 years old. This was the average life-span of the members of his community, thus making him the example in this respect also. 
Despite this characteristic being common to all Prophets, false stories about Job and Moses, either borrowed from Israelite sources or misunderstandings of Qur'anic verses, have found their way into Qur'anic commentaries.
In a hadith, God's Messenger says: "The Prophets undergo the severest trials; the greatest misfortunes strike them. Then come other believers; the firmer their belief, the bigger their misfortune." Prophet Job is praised in the Qur'an as a steadfast, excellent servant of God, one ever-turning to his Lord (38:44). As can be deduced from the Qur'anic verses, and mentioned in the Bible, he was afflicted with a skin disease, which caused painful sores from the soles of his feet to the top of his head (Job 2:7). Influenced by Israelite stories, some Qur'anic commentators have added that worms lived in his sores or abscesses, and that the resulting offensive odor caused people to leave him.
These additions are completely groundless. If people really left him, this might have been due to his later poverty. In the beginning, Job was a rich, thankful servant of God; later on, he lost his wealth and children. As a Prophet, he could not have had a repulsive or disgusting appearance, with, at least, his face exempt from sores. Nor could his body have emitted an offensive smell. Contrary to the Biblical account that he cursed the day of his birth (Job, 3:1) and God openly (Job, 7:20-21), and justified himself rather than God (Job, 32:2), Job bore his afflictions for years without any objection. He prayed: Affliction has visited me, and You are the Most Merciful of the Merciful (21:83). God answered his prayer and removed his affliction, and restored to him his household and the like thereof along with them (21:84).
Moses' Speech Impediment
The Qur'an states that Moses, on receiving the order to go to Pharaoh, supplicated: My Lord, open my breast (relieve my mind and enable me to bear everything), and ease for me my task. Loosen a knot upon my tongue so that they may understand my words (20:25–28). Some commentators, influenced by Israelite sources and misunderstanding Moses' supplication, have asserted that he had a speech impediment. According to them, a young Moses once pulled Pharaoh's beard. Angered, Pharaoh wanted to have him killed. But his wife, trying to save the child, asked Pharaoh to test him to see whether he was fit to be judged or decide in his favor. Bringing a weighing scale, the put a piece of gold in one pan and some embers in the other. Moses put the embers in his mouth, which gave him a permanent stutter. So, according to these interpretations, Moses was asking God to remove his stutter.
An invented story cannot serve as the basis for interpreting a Qur'anic verse. If Moses had had such a speech impediment, he should have prayed for the knot—not a knot—to be loosened. What Moses was asking for was a greater ability to articulate God's Message in Pharaoh's presence, for he was not as eloquent as his brother Aaron (28:34; Exodus 4:10).
In conclusion, all Prophets were both physically and mentally perfect. Regardless of what others might claim, there is nothing in their lives to suggest even the slightest defect. However, some of them may have been superior to others in certain respects: And those Messengers, some We have preferred above others; some there are to whom God spoke [directly], and some He raised in rank (2:253). Prophet Muhammad is superior to all of them by virtue of being the last Prophet sent to both humanity and jinn. His Mission was not restricted to a certain people or a certain time; rather, it was directed toward all people and remains valid until the end of time.
 The Letters, 2:84–5.
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