The Landmarks of Sincerity in Action

Question:
What are the factors that affect an action so that it is not sincere? For example, what kinds of actions can enter into an action and corrupt or weaken its sincerity for Allah the Exalted? What are they?

Answer:
If an action is based on shirk (associating partners with Allah), then its foundation is invalid from the start, and nothing of it reaches Allah, and its doer is not rewarded for it. However, if the action is originally for Allah the Glorious and Exalted, and the person is directing himself to Allah the Glorious and Exalted, but something of riya' (showing off in worship) and love for people's praise enters the heart of its doer, then this is considered a corrupter of the action. Yes. Because it is an obstacle that arose for the action and corrupted it, like an illness that arises for a fruit, or for a body, and if it persists with it, it corrupts and invalidates it because it is a serious obstacle. In the hadith, the Prophet (peace and blessings be upon him) informed about three men who performed actions that are among the best actions, yes, and yet they were dragged into the Fire, I seek refuge in Allah, on their faces. Why? One of them was a mujahid who was fighting, and he appeared to be fighting in the cause of Allah and was killed. So on the Day of Resurrection, Allah the Glorious and Exalted asks him, and he says, "I fought for You and I killed." Hmm. Allah says, "You lied, but you fought so that it would be said, 'He is brave' or 'He is courageous,' and that was said." The second, Allah asks him about the wealth He gave him, "What did you do with it?" He says, "I did not leave anything that You would love to be spent in, except that I spent in it." Allah says, "You lied, but you spent so that it would be said, 'He is generous,' and that was said." Then he is ordered to the Fire, I seek refuge in Allah. The third came as a learner and a teacher, and Allah the Glorious and Exalted asks him, "What did you do? What did you do with your knowledge?" He says, "O my Lord, I learned the Qur'an for You, I learned the Qur'an for You, and I taught it for You." Allah says, "You lied, but you learned so that it would be said, 'He is a scholar,' and that was said." Then he is ordered to the Fire. This indicates that the appearance of the action is not what is considered. Also, a person may perform an action that contains no shirk, no apparent shirk, and no riya', but he intends by it a desire from the desires of this world and its ruins. This is an invalid action, and its doer is in the Fire, as He said, the Exalted and Glorified: and they are not deprived therein. Those are the ones who have no share in the Hereafter except the Fire, and their deeds are rendered worthless, and what they used to do is invalid. Hijrah is among the best actions, but if the intention of its doer is a desire from the desires of this world, it does not benefit him with Allah at all, as came in the hadith: