If Satan could not succeed in this...
If Satan could not succeed in this, he would try to falsify one's worship by way of causing him to pretend holiness: by slighting the worships of the people in his eyes, and by causing him to regard the people indifferent [heedless]. Then he induces him to spend all his life on matters such as the niyyah , which is inseparable from the act, or the takbīr or the recitation, which are common and ordinary acts.
At any rate, Satan would not leave man alone before nullifying his worship by one way or another. Satanic whisperings come through diverse ways, which we cannot discuss for the time being, nor scrutinize them all. But the whispering in the niyyah , from among them, may be the most ridiculous and the strangest, because if someone tried, with all his powers, to do a voluntary act in all his life, without a niyyah [an intention], it would be impossible for him to do it.
Nevertheless, you may find some wretched, sick and feeble-minded person who spends a considerable time at every Salat just to have a firm intention. Such a person is more like the one who thinks a long time whether he is to decide to go shopping or to go for a lunch.
This helpless man, to whom the Salat should be his ascension to His proximity, and the key to his happiness, and, by applying its cordial disciplines and realizing the secrets of this divine grace he should perfect his essence [ dhāt ] and secure his growth [ nash'ah ] of life, he, on the contrary, neglects all these matters, or, much worse, besides regarding them unnecessary, he takes them all to be false, and uses his dear and valuable capital to serve Satan and to obey his slinking whispers, placing the God-given reason [' aql ], which is the light of guidance, under the rule of Iblīs .
'Abdullāh ibn Sinān says: “I mentioned before Imām as-Sādiq (' a ) [a case concerning] a man who was afflicted with frequently performing the Wudu' and the Salat , and described him to be a man of reason.
The Imām said: “What reason has he in obeying Satan?” I asked him: “How is it that he is obeying Satan?” He said: “If you ask him wherefrom his hesitation comes to him, he will tell you it is of the work of Satan.”[^1] In short, man should uproot this by whatever means of austerity and strife, for it deprives him of all happiness and good.
It may be that forty years of a man's worship are not correctly performed even in the outer appearance or according to the juristic formal details, let alone the internal religious disciplines.