Eighteen Treatises from the Mishna, by D. A. Sola and M. J. Raphall, , at sacred-texts.com
§ 1. Men are not to stand up and pray, except with profound humility. The pious men of ancient days used to pause a full hour before they began to pray, in order to direct their minds [hearts] to the Deity. Though the king salute him he is not to respond [to the salutation] and though a serpent wind itself round his heel, he is not to interrupt [his prayers].
§ 2. The [divine] power of [causing] the rain [to descend] must be mentioned in [the benediction for] the resurrection of the dead. Supplication for rain is to be made in the benediction for the year, and הבדלה, [the distinction between the Sabbath and week day] in the benediction חונן הדעת [who graciously bestows knowledge]. R. Akivah saith the הבדלה is to be said in a fourth benediction by itself. R. Eleazar saith, in the thanksgiving [מודים].
§ 3. He who says in his prayers "Thy mercy extends [even] to a bird's nest, or for the good [which thou doest us] be thy name remembered," or he who says twice מודים [we thank] is to be silenced. If a man step up to the ark [as minister to pray for the congregation] and make a mistake, another shall step up in his stead; nor may he in such a case, decline the office. From whence does he [the substitute] begin? From the commencement of the benediction in which his predecessor made the mistake.
§ 4. He who steps up to the ark is not to respond "Amen" after the Cohanim [priests], lest his attention become diverted [from the prayers]. If no other Cohen be present but himself, he is not to lift up his hands [to bless the congregation]. But if he feel quite assured that he can lift up his hands, and then resume [his prayers], he is at liberty so to do.
§ 5. If a man prays and makes a mistake, it is a bad omen for him. If he be deputed by a congregation [minister], it is a bad omen for his constituents, for a man's deputy is like the man himself. It is related of R. Hanina ben Dosa, that when he prayed for the sick, he would say, "This one will live," or "Such a one will die." They [the sages] said to him, "By what dost thou know [it]?" He said to them, "If my prayer is fluent in my mouth, I know that he is accepted; but if not, I know that he is lost!"