Why does intention (niyyah) matter so much in Islam?

On the Day of Judgement Allah will decide on the sincerity of the deed. Consider the first hadith of Sahih Bukhari: “The reward of the deeds depends upon the intention” [Sahih al-Bukhari 1]

Just as the body comprises the material and the immaterial, the physical body and the soul, there is an external aspect and an internal aspect to every action: the intention with which the deed is performed, for whom it is performed, and why it is performed, the motive behind that deed.

The soul does not need words. It has a silent language of its own, linked to the inner state of the heart, and that inner state decides the destiny of a deed.

Once a man questioned Shaykh ul Hadith Zakriya rahimahullah about Tasawwuf. Shaykh Zakriya’s rahimahullah answer was plain and clear, “The beginning of Tasawwuf is the Hadith that ‘deeds are dependent upon their intentions’ (‘Innamul a’mal o binnyat’) and the epitome is that you worship Allah as you see Him (Ihsan)”.