Wallatheena la yadAAoona maAAa Allahi ilahan akhara wala yaqtuloona annafsa allatee harrama (surah Furqan: 68)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(25:68) who do not invoke any god but Allah nor kill a soul, which Allah has forbidden, unjustly, nor commit adultery. *84 -He who does this shall be punished for his sin,

Wallazeena laa yad`oona ma`al laahi ilaahan aakhara wa laa yaqtuloonan nafsal latee harramal laahu illaa bilhaqqi wa laa yaznoon; wa mai yaf`al zaalika yalqa asaamaa

*84) The true servants refrain from three great sins: Shirk, murder and adultery. The Holy Prophet himself warned of their gravity. According to 'Abdullah bin Mas`ud, when some one asked him about the worst sins, he replied, (1) "It is to set up someone as equal in rank with Allah, Who has created you, (2) to kill your own child for fear of its sustenance, and (3) to commit adultery with the wife of your neighbour." (Bukhari, Muslim, Tirmizi, Nasa`i, Ahmad). Obviously this is not a complete list of the "heinous sins". But these three instances have been cited because they were most prevalent in the Arab society of those days .
As regards the inclusion of refraining from shirk among the excellences of the true servants, one may ask why it should be presented as virtue before the disbelievers who did not regard shirk as a vice. It is because the Arabs had doubts about the doctrine of shirk even though they appeared to be deeply involved in it. This is amply supported by their history. For instance, when Abraha invaded Makkah, the Quraish did not invoke their idols to save the Ka`bah from him, but they begged Allah to save it. Their contemporary poetry bears sufficient evidence that they regarded the destruction of the "people of the elephant" due to Allah's power and supernatural interference and not due to any help of their idols. The Quraish and the polytheists of Arabia had also come to know that when Abraha reached Ta`if on his way to Makkah, the people of Ta`if had offered him their services to destroy the Ka`bah and had even provided him guides to take him safely to Makkah through the hills, for fear that he might also destroy the temple of "Lat", their chief deity. This event so much offended the Arabs that for years after this they continued , pelting the grave of the chief guide with stones for retaliation. Moreover, the Quraish and the other Arabs attributed their creed to Prophet Abraham and looked upon their religious and social customs and their Hajj rites as part of Abraham's religion. They knew that Prophet Abraham was a worshipper 'of Allah and not of idols. They also had traditions to show as to when they had started idol-worship, and which idol had been brought from where, when and by whom. The fact is that the common Arab did not have much of reverence for his idols. He would even speak insultingly of it and withheld his offerings when it failed to fulfil his wishes and prayers. For instance, there is the story of an Arab who wanted to avenge the murder of his father. He went to the temple of his idol, Zul-Khalasah, and wanted to take an omen. The response came that he should abandon his intention. At this the Arab became furious and cried out: 'O Zul-Khalasah! Had you been in my place, and your father was murdered, you would not have said that the murderers should not be punished." Another Arab took his herd of camels to the shrine of his god, named Sa'd, for seeking its blessings. It was a tall idol which had been smeared with sacrificial blood. On seeing it, the camels became terrified and started running in all directions. The Arab was so filled with rage that he started pelting the idol with stones, shouting, "May God destroy you ! I had come to you to seek blessings for my camels, but you have deprived me of all of them." There were certain idols about whose origin filthy stories were current. For instance, the story about Asaf and Na'ilah whose images had been placed at Safa and Marwa, was that they were actually a man and a woman, who had committed adultery inside the Holy Ka`bah and had been turned into stone by God as a punishment. When the deities had such reputation, no worshipper could cherish any reverence for them in his heart. From this one can easily understand that the Arabs did recognize the value of true God-worship deep in their hearts, but, on the one hand, it had been suppressed by ancient customs and ways of ignorance, and on the other, the priestly class among the Quraish had vested interests, who were busy creating prejudices against it among the people. They could not give up idol-worship because such a step would have brought to an end their supremacy in Arabia. That is why, refraining from shirk and worship of One AIlah has been mentioned as a mark of superiority of the followers of the Holy Prophet without any fear of contradiction by the disbelievers, for even they in their heart of hearts knew that it was a weighty argument against them.