Moslem has quoted from Ayesheh in his book, Sahih, in passengers Namaz chapter: When Allah necessitated Namaz, it was two rakat (part of Namaz), and then He necessitated it to be done complete (4 rakats) homeland, but it must be done in travel like the first time it was ordered. (Moslems Sahih, v.2, p.142)
And also Moslem has quoted from Yaeli ibn Omayeh in the same book that: I told Omar ibn Khattab: when those days they frightened atheists and they did not do Namaz in complete form, nowadays, they are in safety, why do they do Namaz half during travel? Omar answered: I was wondered about it, too, so I asked the Prophet (peace be upon him and his relatives) about its reason. He said: it is the favor that Allah made for you, and then accept His alms. (Moslems Sahih, v.2, p.143)
Again, Moslem has quoted from Ibn Abbas, in his book, Sahih, that he said: Allah necessitated Namaz on the Prophets (peace be upon him and his relatives) tongue in homeland four rakats, during travel 2 rakats, and in frightening situation 1 rakat. (Moslems Sahih, v.2, p.143)
He has quoted from Anas ibn Malik, too, he said: when the Prophet (peace be upon him and his relatives) reached 3 farsang (unit of length), he did his Namaz two rakats. (Moslems Sahih, v.2, p.145)
And also he narrated that: he was in a trip between Medina to Mecca with the Prophet (peace be upon him and his relatives), so he did his Namaz in two rakats until we came back. Narrators asked: how long were you in Mecca? He said: Ten days! (Moslems Sahih, v.2, p.145)
From the hadiths that Moslem mentioned in his Sahih, it shows the Quranic order for doing Namaz half in travel can be understood out of it, so the Prophet (peace be upon him and his relatives) found out this order from that Quranic Verse and he said and did it. And he said that it was Allahs favor and alms that Muslims had to accept it and follow it. So this point rejected Dualibi and his followers claims for making excuse for Omar to make his mistakes correct As they said Omar looked at the reason of order not the appearance of it. Because the order that comes for Namaz was to do it in half, and Omar became astonished about it and the Prophet (peace be upon him and his relatives) made him understand the order the Allahs order does not stop because of its reason, so Namaz is half during travel even though people are in safety and they did not frighten from atheists. But Omar gave another idea (fatwa), against the idea tha Dualibi and his followers believed.
Now, Osman ibn Affan should be considered, certainly he made his own idea out of the exact text of Quran and the Prophets (peace be upon him and his relatives) hadiths, so he could reach to the previous caliphs actions. When he sat in the caliphate chair, he announced that Namaz had to be done complete during travel! It means instead of two rakats, it should be done four rakats.
I contemplated a lot about it, and I did not find the reason for this change, except that they wanted to present himself to people especially Bani Omayeh, as a more pious person than Mohammad (peace be upon him and his relatives) Abu Bakr, and Omar.
Moslem has quoted from Salam ibn Abdollah, in his book, Sahih, in Namaz and its halfness, that the Prophet (peace be upon him and his relatives) in Mana, and other places did Namaz two rakats, and Abu Bakr and Omar did Namaz the same way, evenOsman at the beginning of his governing did the same but then he ordered to do Namaz in four Rakats. (Moslems Sahih, v.2, p.145)
And also, Moslem has quoted from Zahari whoasked Arvah: Why did Ayeshe do Namaz completely in travel? He said: she made her idea (ijtehad) as Osman did it. (Moslems Sahih, v.2, p.143)
So in this way, Allahs religion, His orders, and His texts changes by the others ideas and interpretations!!