Prophets(Aliahi Salam) are Sinless

Let us see the Tafsir of the aayat “17:39”

[Tafsir Ibn Kathir

Allah says: `What We have commanded you to do is part of good manners, and what We have forbidden you are evil qualities. We have revealed this to you, O Muhammad, so that you may command the people likewise.’

﴿وَلاَ تَجْعَلْ مَعَ اللَّهِ إِلَـهًا ءَاخَرَ فَتُلْقَى فِى جَهَنَّمَ مَلُومًا﴾

(And set not up with Allah any other god lest you should be thrown into Hell, blameworthy) meaning, your own self will blame you, as will Allah and His creation.

﴿مَّدْحُورًا﴾

(rejected) means far removed from everything good. Ibn `Abbas and Qatadah said: “(It means) cast out.” This is an address to the Ummah via the Messenger , for he is infallible.(Sinless)

Tafsir Ibn Kathir

Sahih Al Bukhari

Volume: 6, Book Number: 60, Hadith Number: 360

Volume: 6, Book Number: 60, Hadith Number: 361

Narrated Aisha: The Prophet used to offer prayer at night (for such a long time) that his feet used to crack. I said, “O Allah’s Apostle! Why do you do it since Allah has forgiven you your faults of the past and those to follow?” He said, “Shouldn’t I love to be a thankful slave (of Allah)?’ When he became old, he prayed while sitting, but if he wanted to perform a bowing, he wound get up, recite (some other verses) and then perform the bowing.