The Chosen Sincere Slaves

إِلَّا عِبَادَكَ مِنْهُمُ الْمُخْلَصِينَ

Except Your slaves among them the chosen ones."
[Al-Quran 38:83]

وَلَقَدْ هَمَّتْ بِهِ ۖ وَهَمَّ بِهَا لَوْلَا أَن رَّأَىٰ بُرْهَانَ رَبِّهِ ۚ كَذَ‌ٰلِكَ لِنَصْرِفَ عَنْهُ السُّوءَ وَالْفَحْشَاءَ ۚ إِنَّهُ مِنْ عِبَادِنَا الْمُخْلَصِينَ

And certainly she did desire him, and he would have desired her, if not that he saw the proof (of) his Lord. Thus, that We might avert from him the evil and the immorality. Indeed, he (was) of Our slaves the sincere.
[Al-Quran 12:24]

وَقَالَ الْمَلِكُ ائْتُونِي بِهِ أَسْتَخْلِصْهُ لِنَفْسِي ۖ فَلَمَّا كَلَّمَهُ قَالَ إِنَّكَ الْيَوْمَ لَدَيْنَا مَكِينٌ أَمِينٌ

And said the king, "Bring to me him." I will select him for myself nafs." Then when he spoke to him, he said, "Indeed, you (are) today with us firmly established (and) trusted."
[Al-Quran 12:54; translation edited in italics to retain the word nafs]

Joseph was one of the عِبَادِنَا الْمُخْلَصِينَ , and thus Satan could not tempt him into sin. Joseph was human, and he could have also desired her, but he was a chosen one, sincere. Surah as-Saaffaat presents examples of the chosen ones (الْمُخْلَصِينَ) while Surah az-Zumar discusses in detail the serving sincerely (مُخْلِصًا) in Deen. 

Kings have their laws and govern according to it. Allah's Laws of Recompense are known as Allah's Deen. Allah chooses whom He wills for His Nafs. In Q20:41, we read Allah informing Moses that He has chosen him for His Nafs. In 12:54, we read about the King of Egypt choosing Joseph for his nafs. 

Joseph was in polytheistic Egypt when these situations arose. Several centuries later, Moses was sent to the Pharaoh of Egypt. In Surah Ghafir, while Pharaoh was conspiring to kill Moses, we read about another man (Q40:28-44), an Egyptian, who was an undeclared believer. He reminds his people that Allah had earlier sent Joseph, and he had foretold the coming of a Messenger (Moses), but later on the people fell in doubt about it after Joseph perished (هَلَكَ). This is perhaps of significance as the Egyptians used to embalm to preserve the dead as mummies. Even though Joseph's body was embalmed, he perished, and as per his will, his bones were taken away from Egypt when Allah rescued the the Bani Israel, and punished the Pharaoh and his people.   

In Q40:44, that Egyptian believer is quoted as stating:  فَسَتَذْكُرُونَ مَا أَقُولُ لَكُمْ ۚ وَأُفَوِّضُ أَمْرِي إِلَى اللَّهِ ۚ إِنَّ اللَّهَ بَصِيرٌ بِالْعِبَادِ  And you will remember what I say to you, and I entrust my affair to Allah. Indeed, Allah (is) All-Seer of (His) slaves." The next two ayaat informs us that: فَوَقَاهُ اللَّهُ سَيِّئَاتِ مَا مَكَرُوا ۖ وَحَاقَ بِآلِ فِرْعَوْنَ سُوءُ الْعَذَابِ So protected him Allah (from the) evils that they plotted, and enveloped (the) people (of) Firaun (the) worst punishment,  النَّارُ يُعْرَضُونَ عَلَيْهَا غُدُوًّا وَعَشِيًّا ۖ وَيَوْمَ تَقُومُ السَّاعَةُ أَدْخِلُوا آلَ فِرْعَوْنَ أَشَدَّ الْعَذَابِ The Fire; they are exposed to it morning and evening. And (the) Day (will be) established the Hour, "Cause to enter (the) people (of) Firaun (in the) severest punishment."

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The above is an excerpt from: Q38 71-88 || Q12