The Arabic word translated as destiny is qadar. In its derivations, this word also means determination, giving a certain measure and shape, dividing, and judging. Muslim scholars of Islam define it as Divine measure, determination, and judgment in the creation of things.
Before discussing Divine Decree and Destiny further, consider the following relevant verses:
With Him are the keys of the Unseen. None but He knows them. He knows what is in the land and the sea. Not a leaf falls but He knows it, not a grain amid the darkness of the soil, naught of wet or dry but it is in a Manifest Book (Kitabun Mubin). (6:59)
There is nothing hidden in the heaven or the Earth but it is in a Manifest Book. (27:75)
It is We Who bring the dead to life. We record what they send (of their lives and conduct to the Hereafter) and what is left of them. All things we have kept in a Manifest Record (Imamun Mubin). (36:12)
They ask: "When (will) this promise (be fulfilled), if you are truthful?" Say: "The knowledge is with God only, and I am but a plain warner." (67:25–26)
Nay, but it is a glorious Qur'an. On a Preserved Tablet (Lawhun Mahfuz). (85:21–22)
In one sense, Decree and Destiny mean the same thing. In another sense, however, Destiny means to predetermine or preordain, while Decree means to implement or put into effect. To be more precise, Destiny means that everything that exists, from subatomic particles to the universe as a whole, is known by God Almighty. His Knowledge includes all space and time, while He Himself is absolutely free both of them. Everything exists in His Knowledge, and He assigns to each a certain shape, life span, function or mission, and certain characteristics.
Consider the following analogy: Authors have full and exact knowledge of the books they will write, and arrange its contents before writing it. In this sense, Destiny is almost identical with Divine Knowledge, or is a of Divine Knowledge. It is therefore also called the "Supreme Preserved Tablet" (or the "Manifest Record"). Destiny also means that God makes everything according to a certain, particular measure and in exact balance:
God knows what every female bears and what the wombs absorb and what they grow. And everything with Him is measured. (13:8)
The sun and the moon are made punctual according to a calculation. The stars and the trees adore, in subservience to Him. And the sky He has uplifted; and He has set the balance, that you exceed not the balance, but observe the balance strictly, nor fall short thereof. (55:5-9)
The universe's exact measure and balance, order and harmony, as well as that of all it contains, clearly show that everything is determined and measured, created and governed by God Almighty. Therefore, Divine Destiny exists. Such assertions as determinism, which is upheld by many people and even some Marxists, to explain this obvious universal order and operation are tacit admissions of Destiny. But we have to clarify one point here: According to Islam, absolute determinism cannot be used in the context of human action.
All seeds, measured and proportioned forms, and the universe's extraordinary order and harmony (which has continued for billions of years without interruption or deviation) demonstrate that everything occurs according to God Almighty's absolute determination. Each seed or ovum is like a case formed by Divine Power into which Divine Destiny inserts the future life-history of a plant or a living being. Divine Power employs atoms or particles, according to the measure established by Divine Destiny, to transform each seed into a specific plant, and each fertilized ovum into a specific living being. This means that the future life-history of these entities, as well as the principles governing their lives, are prerecorded in the seed or the fertilized ovum as determining factors and processes.
Plants and living beings are formed from the same basic materials. However, there is an almost infinite variety between species and individuals. Plants and living beings grow from the same constituent basic elements, and display great harmony and proportion. And yet there is such abundant diversity that we are forced to conclude that each entity receives a specific form and measure. This specific form and measure is established by Divine Destiny.