First: Speaking, even if accidentally or in sleep; because engaging in what is not permissible in prayer invalidates it, whether done intentionally or forgetfully, whether little or much: such as eating and drinking. It was reported from Muawiyah ibn al-Hakam, may Allah be pleased with him, that the Prophet, peace be upon him, said: "Indeed, this prayer is not suitable for any of the speech of people; it is only for glorification, takbir, and recitation of the Quran," in Sahih Muslim 1: 381, and Sahih Ibn Khuzaymah 2: 35, and Sahih Ibn Hibban 6: 23. And from Zayd ibn Arqam, may Allah be pleased with him, who said: "We used to speak during prayer, and a man would talk to his companion next to him in prayer until the verse was revealed: (And stand before Allah in obedience) Al-Baqarah: from verse 238, so we were commanded to be silent and forbidden from speaking," in Sahih Muslim 1: 383. Second: The salutation (salam): If one greets to exit the prayer, his prayer is invalidated if he intentionally greets. However, if the greeting was accidental, it does not invalidate it; because greeting is among the remembrances, and in the case of forgetfulness, it is considered a remembrance, while in the case of intention, it is considered speech. If he greets someone while in prayer, his prayer is invalidated whether he did so intentionally or forgetfully. Third: Responding to a greeting in any case: It invalidates the prayer whether done intentionally or forgetfully; because responding to a greeting is not among the remembrances, but it is speech and conversation, and speech invalidates the prayer whether done intentionally or forgetfully. Jabir, may Allah be pleased with him, said: "We were with the Prophet, peace be upon him, and he sent me on an errand, and I returned while he was praying on his mount, facing a direction other than the Qiblah. I greeted him, but he did not respond to me. When he finished, he said: "Nothing prevented me from responding to you except that I was praying," in Sahih Muslim 1: 384, and Sahih al-Bukhari 1: 407. Fourth: Groaning, moaning, and sighing: Groaning is saying "Ah, Ah," and moaning is saying "Oh," and all of these invalidate the prayer, except if one is sick and cannot help but groan or moan; because his groaning then is like sneezing if it involves letters. Ibn Abbas, may Allah be pleased with him, said that the Prophet, peace be upon him, said: "Blowing in prayer is speech," in Musannaf Ibn Abi Shaybah 2: 67, and Musannaf Abdul Razzaq 2: 189, and its chain is authentic. See: I'la al-Sunan 5: 51. And Abu Huraira, may Allah be pleased with him, said: "Blowing in prayer is speech," in Musannaf Abdul Razzaq 2: 189. Fifth: Crying out loud due to pain or calamity: Except if the crying is for matters of the Hereafter: such as crying from the mention of Paradise or Hell, then it does not invalidate his prayer; because such crying indicates an increase in humility, which is the aim of prayer, and it is akin to glorification or supplication. Abdullah ibn al-Shakheer, may Allah be pleased with him, said: "I saw the Messenger of Allah, peace be upon him, praying and there was a sound in his chest like the sound of a boiling pot from crying," in Sahih Ibn Hibban 3: 30, and Al-Mustadrak 1: 396, and Musnad Ahmad 4: 25, and Sha'b al-Iman 1: 481.
Sixth: Clearing the throat without an excuse: If it is not prompted by necessity, and it involves letters, it invalidates his prayer; because speech is what is uttered, and if it is with an excuse, such as being prompted by necessity, it does not invalidate his prayer; due to the impossibility of avoiding it. Seventh: Saying "May Allah have mercy on you" to someone who sneezes; because it falls under the conversations of people. Eighth: Responding to bad news with the statement of patience — saying: "Indeed, we belong to Allah and indeed to Him we will return" — and responding to good news with praise, and expressing amazement with the glorification and declaration of faith — saying "There is no god but Allah" — but if he does not intend to respond, and he meant to inform him that he is in prayer, it does not invalidate it; Jabir, may Allah be pleased with him, said: "The Messenger of Allah, peace be upon him, sent me while he was heading to Banu al-Mustaliq, and I came to him while he was praying on his mount, and I spoke to him, and he gestured with his hand: like this, then I spoke to him again, and he gestured: like this, and I heard him reciting while he was nodding his head, and when he finished, he said: What did you do with what I sent you for? Nothing prevented me from speaking to you except that I was praying," in Sahih Muslim 1: 383. Ninth: Opening up to someone other than his imam: However, opening up to his imam does not invalidate the prayer of the one who opens and the imam, even if he opens after the imam has recited what is sufficient for prayer, or has moved to another verse according to the correct view, although it is preferable to refrain from opening here; Ibn Umar, may Allah be pleased with them, said: "The Prophet, peace be upon him, prayed a prayer in which he was reciting, and he became confused, and when he finished, he said to Ubayy ibn Ka'b: He said: Yes, he said: What prevented you from opening for me?" in Sunan al-Bayhaqi al-Kabir 3: 212, and Musnad al-Shamiyeen 1: 437, and Al-Mu'jam al-Kabir 12: 313, and its narrators are trustworthy as mentioned in Majma' al-Zawa'id 1: 169. See: I'la al-Sunan 5: 56. And Ali, may Allah be pleased with him, said: "If the imam asks you to feed him, then feed him," in Musannaf Ibn Abi Shaybah 1: 417, and the Hafiz authenticated it in Al-Talkhis 1: 284. And Ibn Mas'ud said: "If the imam becomes confused, do not respond to him, for it is speech," Al-Haythami said in Majma' al-Zawa'id 2: 69: It was narrated by Al-Tabarani in Al-Kabir and its narrators are the narrators of the authentic hadith. Tenth: Reading from the Mushaf; because taking from the Mushaf is considered external learning, and it invalidates the prayer whether the Mushaf is held or placed, and whether the praying person turns its pages or someone else turns them; Ibn Abi Awfa, may Allah be pleased with him, said: "A man came to the Prophet, peace be upon him, and said: O Messenger of Allah, I cannot learn the Quran, so teach me what suffices me from the Quran. He said: Say: Glory be to Allah, and praise be to Allah, and there is no god but Allah, and Allah is the Greatest, and there is no power and no strength except with Allah," in Sahih Ibn Hibban 5: 116, and Sunan Abu Dawood 1: 220, and Sunan al-Bayhaqi al-Kabir 2: 381, indicating that whoever has the Quran should recite what is easy for him. If he is unable to learn it and memorize it to the extent that suffices for prayer, he should move to remembrance as long as he is unable, and none of the imams have stated, as far as we know, that it is obligatory for him to read from the Mushaf. If reading from the Mushaf were permissible in prayer and did not invalidate it as some claim, it would be obligatory for the one unable to memorize; because he is capable of reading in a way that he is not unable to do, and moving to remembrance is only after confirming the inability to read from the Mushaf. Thus, it is established that reading from the Mushaf does not constitute a reading that validates the prayer. Eleventh: Supplicating for what one asks of people, such as: O Allah, marry me to so-and-so, or give me a thousand dinars, it invalidates the prayer if done before the Tashahhud, but after the Tashahhud, it does not; because the essence of people's speech after the Tashahhud does not invalidate the prayer, so how about what resembles it. Twelfth: Eating and drinking; because they contradict prayer, and there is no difference between intention and forgetfulness, all of it invalidates the prayer; because the state of prayer is a reminder; because it is in a form that contradicts the norm; due to the necessity of purity, entering into a state of ihram, humility, facing the Qiblah, and transitions from one state to another while refraining from speech, which is like breathing, and all of this occurs in a short time, so eating and drinking are extremely distant and thus are not excusable. Thirteenth: Any excessive action: The criterion for excessive action that invalidates the prayer is what the observer knows that the doer is not praying. As for minimal action, which is the opposite of excessive, it is excused, and the prayer is not invalidated by it; because its origin cannot be avoided; because there are movements in the living that are not part of the prayer by nature, so it is excused as long as it is not excessive and does not enter into the limit of what can be avoided. Thus, intention and forgetfulness are equal in this regard; Abu Qatadah, may Allah be pleased with him, said: "The Messenger of Allah, peace be upon him, was praying while carrying Umamah bint Zainab, the daughter of the Messenger of Allah, peace be upon him, and Abu al-As ibn al-Rabi. When he stood, he would carry her, and when he prostrated, he would place her down," in Sahih Muslim 1: 385, and Sahih al-Bukhari 1: 193. And Aisha, may Allah be pleased with her, said: "I used to sleep between the hands of the Messenger of Allah, peace be upon him, with my legs facing the Qiblah, and when he prostrated, he would nudge me, so I would retract my legs, and when he stood, he would spread them out," in Sahih al-Bukhari 1: 192, and Sahih Muslim 1: 367, and nudging is touching or squeezing with the tips of the fingers. See: Al-Bahr 2: 8-9, and Fath Bab al-'Inayah 1: 301, and Rad al-Muhtar 1: 414.