It has been reported, that the Messenger of Allah (saws) once found the companions arguing about Qadar. He forbade them from indulging in such a debate and told them that communities before them had been destroyed for that reason.

However, by the grace of Allah (swt), our pious predecessors were able to understand the issue and form a moderate view based on equity and justice. In their understanding, the issue of Qadar and Qada stems from the Unity of Allah's attribute of Cherishing (Tawhid ar-Rububiyah). This is one of the three kinds of Allah's unity:

1. Unity of Divinity (Tawhid Al-Ulahiyah), which is to direct all forms of worship to Allah alone.
2. Unity in the matter of the Lordship of Allah (Tawhid ar-Rububiyah), which means to believe that all creation, sovereignty and planning belong to Allah (swt).
3. Unity in the matter of Allah's names and attributes and that these names and attributes are exclusively for Allah (swt). (Tawhid al-Asma was-Sifat).

Imam Ahmed has said:

"Qadar (pre-estimation) is the power of Allah. It is one of the secrets which no one except. Allah knows, as it has been recorded in the well-guarded tablet. We do not know what Allah has destined, either for or against us of concerning all his creation, except after the event has occurred or has been told by the Prophet himself."

The actions done by all the creatures that have the power of will.

"These actions are a consequence of their efforts and their choice, a power that has been given to them by Allah. He thus says in the Qur'an: To whoever among you wills to go straight....." Qur’an 81:28

".....Among you are some that hanker after this world And some that desire the Hereafter......." Qur’an 3:152

Man knows very well the difference between what he does from his own free will and what he does because of external force. The person who reaches safely the bottom of a flight of stairs knows that this is because he walked down carefully. However, if he is pushed down from the top, he has no power over how he lands at the bottom. The first instance is an example of choice: the second is clearly one of compulsion. Similarly, a person who suffers from incontinence of urine knows that the urine is passed without his will and that if he did not have this illness, he would be able to control the discharge. The difference between the two requires no further explanation.

It is a mercy of Allah that there are certain actions, which are in the voluntary power of the individual but are recorded as if they are not, and so he is not held answerable for them, eg. actions done out of forgetfulness of during sleep. Allah says in the story of the People of the Cave:

".....And we turned them on their right and on their left sides......" Qur’an 18:18

The men themselves are turning over, but Allah Almighty attributes their movements to Himself, since a sleeping person has no control over his actions.

The Prophet (saws) said:

"The one who forgets while fasting and eats or drinks, he should complete his fast because Allah is the one who feeds him and gives him the drink."

"And His Companions (angels) will say: "Here is (his Record) ready with Me!" (And it will be said): "Both of you throw (Order from Allah to the two angels) into Hell, every stubborn Disbeliever (in the Oneness of Allah, in His Messengers etc.) "Hinders of Good, transgressors, doubters, who set up another ilah (god) with Allah, cast him in the severe torment.’ His Companion (Satan -devil) will say: "Our Lord! I didn’t make him transgress. But he (himself) was far astray." He will say: "Dispute not with each other in My presence: I had already in advance sent you warning. The Word changes not before Me, and I do not the least injustice to My servants." Qur’an 50:23-29

Almighty Allah, clearly states that the punishments He inflicts are not cruel but just, since He has already warned His creatures and sent them guidance. He has clearly defined the two paths of piety and disobedience, just as He has defined the consequences of following each path. Man thus has total freedom to choose either path, remembering that if he opts for the path of disobedience, he will not have the excuse to offer Allah on the Day of Judgement.

The Qur’an says in this regard:

"Apostles who gave good news, as well as warning, that mankind, after (the coming) of the apostles, should have no plea against Allah". Qur'an 4:165

The Qur’an and reality also refute those who go to the other extreme of giving Man complete freedom of action, leaving no role for Allah. We are told that the will of Man follows the will of Allah:

"To whoever among you wills to go straight. But you shall not "will" except as Allah wills, - The Cherisher of the Worlds." Qur’an 81:28

"And your Lord creates whatsoever He wills and chooses, no choice have they (in any matter). Glorified be Allah and Exalted above all that they associate as partners (with Him)." Qur’an 28:68

"Allah calls to the home of peace (i.e. Paradise, by accepting Allah’s religion of Islamic Monotheism and by doing righteous good deeds and abstaining from polytheism and evil deeds) and guides whom He wills to a Straight Path." Qur’an 10:25

Those that hold this view are thus rejecting Allah’s Omniscience, one of His essential attributes, by effectively claiming that His Kingdom, there are many things which He does not wish or does not create. But Allah the Magnificent wills everything, creates everything and predestines for everything! It is impossible to conceive of anything happening that He does not wish to happen. This poses problems for us, such as what is the fate of someone whom Allah wished to misguide? It surely cannot be his fault that he did not receive the message of truth. The answer is that Allah guides those who want to be guided, and misguides those who do not wish to receive guidance. We read this in Qur’an:

"........So when they turned away (from the Path of Allah) Allah turned their hearts away (from the Right Path) and Allah guides not the people who are fasiqun (rebellious, disobedient to Allah)." Qur'an 61:5

"So because of their breach of their covenant, We cursed them, and made their hearts grow hard. They change the words from their (right) places and have abandoned a good part of the Message that was sent to them.............." Qur'an 5:13

In other words, the wish to be pious emanates from the individual himself and Allah guides him because of this. The issue can be further explained by comparing it to the acquisition of knowledge or to the earning of a living. Allah has decreed the amount of understanding or wealth a person will be able to acquire in his life. This does not mean that the individual can thus sit at home and wait for the wealth or learning to come walking into his arms: only when he goes out searching for it and works hard for it will he get it. The amount of wealth or learning he receives will be proportional to the effort put in, and this is just as true for guidance.

The Prophet (saws) said in this regard:

"Verily, the creation of each one of you is brought together in his mother’s belly for forty days in the form of seed, then he is a clot of blood for a like period, then a morsel of flesh for a like period, then there is sent to him the angel who blows the breath of life into him and who is commanded about four matters: to write down his means of livelihood, his life span, his actions, and whether happy or unhappy."

Allah’s decree and predestination has four components:

The first is Knowledge - Man must believe with total certainty that Allah has knowledge of everything; He knows a minute as well as the general detail of all that happens, whether it is of His own doing or of His creatures.

The second constituent of Qadar is Writing -Allah has written all His knowledge of the fate of His creature in the Preserved Tablet, as He tells us in the Qur’an:

"Know you not that Allah knows all that is in the heavens and on earth? Verily, it is (all) in the Book (Al-Lauh -Al -Mahjfuz). Verily! That is easy for Allah." Qur’an 22:70

http://www.missionislam.com/knowledge/Qadar.htm