The Talmud, by Joseph Barclay, , at sacred-texts.com
1. The morning prayer may be said till noon. R. Judah says "until the fourth hour." The afternoon prayer until the evening. R. Judah says "until half the afternoon." The evening prayer has no limit, and the additional prayers may be said all day. R. Judah says "until the seventh hour."
2. R. Nechooniah, son of Hakanah, used to pray when he entered the lecture-room, and when he went out he said a short prayer. The (Sages) said to him, "what occasion is there for this prayer?" He said to them, "when I enter I pray that no cause of offence may arise through me; and when I go out I give thanks for my lot."
3. Rabban Gamaliel said, "one must daily say the eighteen prayers." R. Joshua said "a summary of the eighteen." R. Akivah said, "if his prayer be fluent in his mouth, he says the eighteen; if not, a summary of the eighteen."
4. R. Eleazar said, "if one make his prayer fixed, his prayer is not supplications." R. Joshua said, "if a man travel in dangerous places, let him use this short prayer: 'Save, O Lord, thy people, the remnant of Israel; at every stage of their journey 1 let their wants be before thee. Blessed art thou, O Lord, who hearest prayers.'"
5. If one ride on an ass, he must dismount: if he cannot dismount, he must turn his face; and if he cannot turn his face, he must direct his heart towards the Holy of Holies.
6. If one be seated in a ship, or in a carriage, or on a raft, he must direct his mind towards the Holy of Holies.
7. R. Eleazar, the son of Azariah, said "the additional 2 prayers are only to be said in a public congregation." But the Sages say, "if there be a public congregation, or no public congregation." R. Judah said in his name, "in every place, where there is a public congregation, individuals are exempted from additional prayers."
54:1 Or transgression.
54:2 Called Musaph.