refuting this suspicion

the polytheists took this verse as a proof for their claims that the prophet has sins and the quran proves that!
" that allah may forgive you your sins of the past and the future, and complete his favor on you, and guide you on the straight path;” ( al fat’h:2)

those polytheists have to know that muhammad’s biography is an open book for everyone and is very huge; everyone reading it can notice that the writers of this biography wrote everything about the prophet’s life in full details. they wrote all about him; when he is sleeping or awake, when he is fighting or in peace times, his prayers and worships, how he is dealing with people and even his life among his family at home.
and when his companions were reporting his speeches ”hadiths” or doings, they were describing the prophet very accurate; as for example describing the way he was sitting or describing his face impressions when talking, so that we can imagine the whole situation as if we can see him in front of us.
in addition to that, the holy quran shows us the prophet’s high qualities:

“and we have sent you (o muhammad ) not but as a mercy for the 'alamin (mankind, jinns and all that exists).“ (al anbia’: 107)

“verily, there has come unto you a messenger (muhammad ) from amongst yourselves (i.e. whom you know well). it grieves him that you should receive any injury or difficulty. he (muhammad ) is anxious over you (to be rightly guided, to repent to allah, and beg him to pardon and forgive your sins, in order that you may enter paradise and be saved from the punishment of the hell-fire), for the believers (he is) full of pity, kind, and merciful.“ (at tauba:128)

and then the quran summarizes all his qualities in this verse:
“and verily, you (o muhammad ) are on an exalted standard of character.” ( al qalam:5)

more than this, the holy quran reported to us even the smallest details of the prophet’s feelings and emotions and what is going on inside his thoughts that no one could know except allah.
as for example allah’s order to the prophet to marry zainab bint jahsh (the x-wife of zaid bin haritha that the prophet used to adopt) for the sake of annulling the habit of adoption.
“and (remember) when you said to him (zaid bin harithah; the freedslave of the prophet) on whom allah has bestowed grace (by guiding him to islam) and you (o muhammad too) have done favour (by manumitting him) "keep your wife to yourself, and fear allah." but you did hide in yourself (i.e. what allah has already made known to you that he will give her to you in marriage) that which allah will make manifest, you did fear the people (i.e., muhammad married the divorced wife of his manumitted slave) whereas allah had a better right that you should fear him. so when zaid had accomplished his desire from her (i.e. divorced her), we gave her to you in marriage, so that (in future) there may be no difficulty to the believers in respect of (the marriage of) the wives of their adopted sons when the latter have no desire to keep them (i.e. they have divorced them). and allah's command must be fulfilled. “ ( al ahzab: 37)

note: the almighty allah annuls the habit of adopting for the sake of protecting relationships. so allah’s ordering the prophet to marry zaid’s x-wife, is to show all muslims in the first place that zeid is not the prophet’s son….but of course in case that he were his son, it would be forbidden to marry the x- wife of one’s son..

from all previous we can see that the prophet’s biography is so detailed and the holy quran speaks even about the hidden details that no one know except allah, and nothing is written in both quran and sunna about any sins committed by the prophet.

those insulters who accuse muhammad(pbuh) that he has sins, are completely blind and hard- hearted because they did not notice the rest of suraht al fat’h that is all about stabilizing the believers and the prophet promising them that they’ll be supported soon and that their victory is very near. so if the prophet were full of sins – as they claim- how would allah promise him victory and show him the right path to follow.

but now lets explain the word “sin” in the verse:
“that allah may forgive you your sins of the past and the future “ ( al fat’h:2)

what is meant by the word “sin” hear is not the meaning that all people know: to commit mistakes and wrong doings, because allah gave all prophets infallibility especially prophet muhammad (pbuh). this fact is known by all prophets’ followers except those who change the words of allah in their holy books especially the jews who are well known in killing and insulting all messengers sent to them.
the “sins” that the quran talks about, are mistakes might be done by a prophet but are no sins that are known to us anyway.

and in addition to all that, muhammad’s reputation before his legation was a very clean one; muhammad was respected by all people; he was honest, moral, with a pure soul and was thus known as “as sadek al ameen” the faithful….

after all that, how dare those insulters to say that muhammad(pbuh) is a sinner!!
“no knowledge have they of such a thing, nor had their fathers. mighty is the word that comes out of their mouths [i.e. he begot (took) sons and daughters]. they utter nothing but a lie.“
( al kahf:5)