If one leaves out a pillar of the prayer, and an explanation of the hadith of Abu Hurayrah (may Allah be pleased with him) regarding the story of Dhu al-Yadayn

The Shaykh : First, if a person says the closing salam before completing his prayer. If he did so intentionally, the prayer is invalid. If he did so out of forgetfulness and then remembered, it is obligatory for him to complete it and then perform the prostration for forgetfulness.
For example: A person prayed the midday prayer, and when he recited the first tashahhud, he continued and completed the tashahhud, then said the salam, while he still had two rak'ahs remaining of the prayer. When he remembered, we say: Come, perform the two rak'ahs. He stood up and prayed the two rak'ahs as usual, then said the salam, then performed the prostration for forgetfulness, two prostrations, and said the salam. Do you understand now? Good. The evidence, the evidence is the hadith of Abu Hurayrah (may Allah be pleased with him): It was as if he was angry, meaning he was not relaxed. He was not relaxed and his chest did not open up. Why? Because he did not complete the prayer. And this is a blessing from Allah upon a person: if a defect occurs in his worship that he is unaware of, he finds himself feeling contracted until He grants him the completion of it. Unlike the person who does not care. The person who strives to perfect his work, if he happens to make a mistake, Allah will make it easy for him to perfect it. The important thing is that when the Companions saw him in this state, and the Messenger of Allah (peace and blessings be upon him) had been given the great awe, the people were afraid to speak to him, even the closest people to him, Abu Bakr and 'Umar, were afraid to speak to him. And there was a man among the people whom the Prophet (peace and blessings be upon him) used to joke with; he called him Dhu al-Yadayn, Dhu al-Yadayn, meaning the one with the two hands, because his hands were long, and the Messenger would joke with him. So the man stepped forward, but he spoke strange words. Words that if you saw philosophers or logicians speaking about them, you would find one turning red and yellow before he even said them. He said: Glory be to Allah. He did not say: I forgot. Nor did he say: The prayer was shortened. He said: Did you forget or was the prayer shortened? There is a third possibility that cannot happen from the Messenger, which is that he intentionally said the salam before completing it. This is from the perspective of logical division possible, but it is not applicable considering the state of what? The Messenger (peace and blessings be upon him).
Now, if I were to say the salam before completing the prayer, it is possible that I forgot, it is possible the prayer was shortened, or what is not possible? As for me, it is not possible. Good, is it possible that I left intentionally or not? It is possible. I am not sinless, I might commit an error. For the Messenger (peace and blessings be upon him), only two things are possible in his case: Did you forget or was the prayer shortened. So what did the Messenger (peace and blessings be upon him) say? He said: . Glory be to Allah. The Messenger says: And everyone knows that he did not pray except two rak'ahs. Does lying occur in the speech of the Messenger? No, by Allah, far from it, and no. But he said that based on his predominant belief. Therefore, we say: whoever says something based on his predominant belief, and the matter turns out to be contrary to what he said, he is not a liar. Even if you swore an oath and the matter turned out to be contrary to what you said, there is nothing upon you, because you are not one who breaks an oath. If you said, for example, based on your belief: By Allah, Zayd will come tomorrow. Do you understand the example? By Allah, Zayd will come tomorrow, meaning what? Zayd will come tomorrow, meaning he will come tomorrow, but he did not come. Is there an expiation upon you? There is no expiation for an oath upon you. Why? Because you swore to what was in your heart, and you believed he would come, but he did not come, so there is nothing upon you. Therefore, the Prophet (peace and blessings be upon him) approved the man who said: He approved him, even though the man did not search all the houses or look. In any case, we return to the fact that the Prophet (peace and blessings be upon him) said: . So he denied a forgetfulness that befalls humanity, and he denied the shortening, which is a legal ruling in which error is not possible. So the man (may Allah be pleased with him) said: . Now the belief of the Messenger (peace and blessings be upon him) and the confession of this man have come together. It needs a judge between them, or does it not? Yes, it needs one. Therefore, he said to the people: He did not take it upon himself, nor did he take the word of the man, as it is possible that he is the one who made the mistake or the man is the one who made the mistake. So the Companions said: .
Pay attention, is the issue clear now? Good.
He prayed the dawn prayer and said the salam in the first rak'ah, then remembered. What does he do? He prayed the dawn prayer and said the salam in the first rak'ah, then remembered. What does he do? He comes with one rak'ah and says the salam, then performs two prostrations and says the salam.
And upon this, it is a secret. Good.