The omnipotence of God is everywhere asserted in the Koran; man's will is totally subordinate to God's will to the extent that man cannot be said to have a will of his own. Even those who disbelieve in Him, disbelieve because it is God who wills them to disbelieve. This leads to the Muslim doctrine of predestination which prevails over the doctrine of man's free-will, also to be found in the Koran. As Macdonald says, " the contradictory statements of the Kuran on free-will and predestination show that Muhammad was an opportunist preacher and politician and not a systematic theologian."
"Taqdir, or the absolute decree of good and evil, is the sixth article of the Muhammadan creed, and the orthodox believe that whatever has, or shall come to pass in this world, whether it be good or bad, proceeds entirely from the Divine Will, and has been irrevocably fixed and recorded on a preserved tablet by the pen of fate." Here are some quotes from the Koran illustrating this doctrine :
liv. 49 All things have been created after fixed decree
iii.139 No one can die except by God's permission according to the book that fixes the term of life.
lxxxvii.2 The Lord has created and balanced all things and has fixed their destinies and guided them
viii.17 God killed them, and those shafts were God's, not yours
ix. 51 By no means can anything befall us but what God has destined for us
xiii.30 All sovereignty is in the hands of God
xiv.4 God misleads whom He will and whom He will He guides
xviii.101 The infidels whose eyes were veiled from my warning and had no power to hear
xxxii.32 If We had so willed, We could have given every soul its guidance, but now My Word is realised - 'I shall fill Hell with jinn and men together.'
xlv.26 Say unto them, O Muhammad: Allah gives life to to you, then causes you to die, then gathers you unto the day of resurrection...
lvii.22 No disaster occurs on earth or accident in yourselves which was not already recorded in the Book before we created them
But there are, inevitably, some passages from the Koran which seem to give man some kind of free-will :
lxxiv. 54 /55 Nay, it is surely a Reminder. So whovever pleases may mind it.
lxxvi.3 We have truly shown him the way; he may be thankful or unthankful.
lxxvi.29 Surely this is a Reminder; so whoever will, let him take a way to his Lord.
xli.16 As to Thamud, We vouchsafed them also guidance, but to guidance did they prefer blindness
xviii.28 The truth is from your Lord : let him then who will, believe; and let him who will, be an unbeliever
But as Wensinck, in his classic "The Muslim Creed", said, in Islam it is predestination that ultimately predominates. There is not a single tradition that advocates free-will, and we have the further evidence of John of Damascus, who "flourished in the middle of the eight century A.D, and who was well acquainted with Islam. According to him the difference regarding predestination and free-will is one of the chief points of divergence between Christianity and Islam." It is evident that, towards the end of his life, Muhammad's predestinarian position hardened; and "the earliest conscious Muslim attitude on the subject seems to have been of an uncompromising fatalism."