Scholars derive from the (Taqdeer - Fate thread
) that destiny is of two types:
a) Muallaq (revocable):
This destiny is written on 'The Preserved Tablet' (al Lawh al Mahfoodh), and is subject to change and alteration through the omission or commission of certain deeds. For example: the lifespan of a person is originally 50 years, but may increase to 60 years if he performs the ritual of Hajj, or a certain calamity is to befall him unless he averts it by spending in charity. This is the destiny refereed to in the aforementioned narration.
b) Mubram (irrevocable):
This destiny denotes the eternal knowledge of Allah. It encompasses the final result of the Muallaq destiny i.e. our choice of actions, their consequences and every precise detail of our lives. This definite knowledge of Allah is not subject to change or alter even slightly and is exclusive to Allah only.
In the light of the above the following may be derived:
Our supplications do change destiny and are of much avail.
Good deeds are a source of increase in ones sustenance, and avert calamities.
Sins result in a decrease in ones sustenance, and invite calamities.
So, as I mentioned in my previous post, riding a motor bike won't kill you, but it can be the cause of ones death. Similarly, smoking won't kill you like a bullet, but eventually the effects of smoking will be the cause of death. So smoking does kill, it just depends on how you view taqdeer.