In 6th Hijri year, Muhammad went to Mecca with other Muslims in order to perform 'Umra (lesser pilgrimage) of Kaba. When he came close to Mecca, he sent 'Uthman to Meccans, in order to tell them that he didn't come to fight, but only in order to perform 'Umra.
Nevertheless, it became famous that Meccans killed 'Uthman (although they didn't kill him). 
Upon hearing the news of 'Uthman's killing, Muhammad gathered Muslims, and asked them to take out their hands and to take a pledge to fight Meccans and to take revenge of 'Uthman's blood. At that point, Muhammad claimed that Jibrael came, and Allah revealed the following verse:

(Quran 48:10
Indeed, those who pledge allegiance to you, [O Muhammad] - they are actually pledging allegiance to Allah. The hand of Allah is over their hands. So he who breaks his word only breaks it to the detriment of himself. And he who fulfills that which he has promised Allah - He will give him a great reward.

But Surprise!!!
'Uthman appeared in the Muslim camp ALIVE later.
Yes, after Allah had already sent Jibrael, who confirmed 'Uthman's death too by telling Muslims that they should take pledge of allegiance at Allah's hand, and after promising them of great rewards for taking revenge of 'Uthman' blood, 'Uthman himself appeared alive in the Muslims camp, and told them that he was not killed. 

Why didn't Allah know that 'Uthman was not killed, but he was alive? When Allah himself started participating in the process of allegiance instead of telling Muslims that 'Uthman was alive, then question arises about Allah's 'knowledge of Unseen'. 

Answer is simple that there exists no Allah in the heavens, but all this was the fabricated stories by Muhammad.
Since Muhammad was a human, and he didn't know the UNSEEN, and he thought that 'Uthman was really killed, thus Allah also thought that 'Uthman was killed.
This proves that: Muhammad = Allah (i.e. Muhammad was Allah himself).

Ibn Kathir writes under the commentary of this verse 48:10:

The pledge mentioned here (in this verse 48:10) is the pledge of Ar-Ridwan which was pledged under a tree, a Samurah, in the area of Al-Hudaybiyyah. The number of the Companions who gave their pledge to Allah's Messenger at that time was either 1,300, 1,400 or 1,500. However, 1,400 is the better choice ...
Muhammad bin Ishaq said in his book on Sirah: "... Umar said to Muhammad:  "We should send Uthman to Abu Sufyan and the chiefs of the Quraysh informing them that you did not come to fight them, but to visit this House and to honor its holiness.' ... Uthman indeed went to Abu Sufyan and the chiefs of Quraysh and imparted the Prophet's message that he was sent with. When `Uthman finished delivering the Prophet's message to them they said to him, `If you wish, you can perform Tawaf around the House.' `Uthman replied, `I would not do that before the Messenger of Allah gets the chance to perform Tawaf around it.' So the Quraysh kept `Uthman waiting in Makkah. However, the Messenger of Allah and the Muslims were told that `Uthman had been killed.'' Ibn Ishaq continued, "I was told by `Abdullah bin Abu Bakr that when news of `Uthman's death was conveyed to him, the Messenger of Allah said, (We will not leave until we fight the people.)'' Ibn Ishaq continued, "The Messenger of Allah called the Muslims to give a pledge of allegiance, resulting in the pledge of Ar-Ridwan being conducted under the tree. ...  Soon afterwards, news came to the Messenger of Allah that the story of `Uthman's death was not true.'' 

Muslim Excuse: There was doubt if 'Uthman was alive or not

Muslim excuse is this that there was a doubt if 'Uthman was alive or not, therefore prophet used his hand on behalf of 'Uthman for taking the pledge. 

Answer: 

Muhammad never made this statement himself that he 'doubted' the killing of Uthman and that was the reason he used his hand on behalf of 'Uthman for taking the pledge. This excuse is being presented by Islam apologists at their own, and it is only based upon their conjecture.  

Moreover, it does not matter if Muhammad doubted his death or not, the main issue is that Muhammad lied about the direct presence of Allah i.e.  while taking the pledge, in order to get the attention and the motivation of the people, Muhammad claimed that Jibrael brought the revelation that people were taking oath of allegiance directly on the hands of Allah, and he will give them great rewards for it.  And when Allah himself participated in the whole process of allegiance instead of telling Muslims that 'Uthman was alive, then question arises about Allah's 'knowledge of Unseen'.