Berakhot 5:50

['One may only stand and begin to pray from an approach of gravity and submission. There is a tradition that the early generations of pious men would wait one hour, in order to reach the solemn frame of mind appropriate for prayer, and then pray, so that they would focus their hearts toward their Father in Heaven. Standing in prayer is standing before God and, as such, even if the king greets him, he should not respond to him; and even if a snake is wrapped on his heel, he should not interrupt his prayer.', 'This mishna speaks of additions to the standard formula of the Amida prayer and the blessings in which they are incorporated. One mentions the might of the rains and recites: He makes the wind blow and the rain fall, in the second blessing of the Amida prayer, the blessing of the revival of the dead. And the request for rain: And grant dew and rain as a blessing, in the ninth blessing of the Amida prayer, the blessing of the years. And the prayer of distinction [havdala], between the holy and the profane recited in the evening prayer following Shabbat and festivals, in the fourth blessing of the Amida prayer: Who graciously grants knowledge. Rabbi Akiva says: Havdala is recited as an independent fourth blessing. Rabbi Eliezer says that it is recited in the seventeenth blessing of the Amida prayer, the blessing of thanksgiving.', 'Concluding the laws of prayer in this tractate, the mishna raises several prayer-related matters. This mishna speaks of certain innovations in the prayer formula that warrant the silencing of a communal prayer leader who attempts to introduce them in his prayers, as their content tends toward heresy. One who recites in his supplication: Just as Your mercy is extended to a bird’s nest, as You have commanded us to send away the mother before taking her chicks or eggs (Deuteronomy 22:6–7), so too extend Your mercy to us; and one who recites: May Your name be mentioned with the good or one who recites: We give thanks, we give thanks twice, they silence him. This mishna and the next one deal with the communal prayer leader. (If one says: “May the good bless You,” this is a path of heresy.) One who is passing before the ark, as prayer leader, and erred, another should immediately pass in his place, and at that moment, this replacement should not refuse in the interest of courtesy. The Amida prayer was interrupted and he should replace him as quickly as possible. From where does the replacement commence? From the beginning of the blessing in which the former had erred.', 'In order to prevent the prayer leader from erring in his prayer, it was said that one who passes before the ark should not respond amen after the blessing of the priests, because of potential confusion. Since the mishna is describing a situation in which he was praying without a prayer book, responding amen would interrupt the order of the prayer and potentially lead him to begin a different blessing. For this reason, even if there is no priest other than the communal prayer leader, he does not lift his hands to bless the people, lest he become confused. And, however, if he is certain that he can lift his hands and resume his prayer without becoming confused, he is permitted to recite the blessing.', 'Concluding its discussion of the halakhot of prayer, the mishna discusses less practical aspects of prayer. One who prays and realizes that he erred in his prayer, it is a bad omen for him; it indicates to him that his prayer was not accepted. And if he who erred is the communal prayer leader, it is a bad omen for those who sent him, because a person’s agent has legal status equivalent to his own. On a similar note, they said about Rabbi Ḥanina ben Dosa that he would pray on behalf of the sick and immediately after his prayer he would say: This one shall recover from his illness and live and this one shall die. When they said to him: From where do you know? He said to them: If my prayer is fluent in my mouth as I recite it and there are no errors, I know that my prayer is accepted. And if not, I know that my prayer is rejected.']