Berachot 26: Source of Additional Prayers and Timelines for Daily Prayers

Ending their conversation about prayer and feces/urine before our next Mishna, the rabbis note that Persian toilets are different.  They are considered to be sealed even if they contain feces, because they are constructed on an incline so that the feces will roll out of the bathroom underground.  Because there is this pipe or canal and no foul smell leaves the bathroom, it is permitted to pray within four cubits.  

The new Mishna states a zav imparts ritual impurity for seven days after a seminal emission.  If he were not a zav, he would only be impure for one day.  A menstruating woman who discharged semen (where she would already be ritually impure before intercourse with her husband) and a woman who engaged in conjugal relations with her husband and later saw menstrual blood will require immersion, but Rabbi Yehuda exempts them.  

Perek III begins with a new Mishna as well: the morning prayer may be recited until noon.  Rabbi Yehuds says that it can only be recited until four hours after sunrise.  The afternoon prayer can be recited until the evening.  Rabbi Yehuda says that it may be recited only until the midpoint of the afternoon (between the point when afternoon sacrifices begin and nightfall, which ends the afternoon)/ . The evening prayer may be recited through the night and is not fixed to a specific hour.  The additional prayer may be recited all day.  Rabbi Yehuda says that it may be recited only until seven hours after sunrise.  

The rabbis discuss what should be done if one omits a prayer at the proper time.  Should a person say two Amida prayers?  Should one continue to pray?  Does it matter if one has intentionally or unintentionally omitted these prayers?  And what about on the eve of Shabbat?  How does reciting havdala, the prayer distinguishing Shabbat from the following day, affect one's obligation to say the Shema?

The rabbis provide proof texts of our forefathers praying in the afternoon or evenings.  For example, Isaac was lasuach, to converse, in the field toward evening (Genesis 24:63); converse means prayer, for Psalms (102:1) teaches that a prayer of the afflicted when he is faint and pours out his sicho, complaint, before the lord".  From this we learn that Isaac was the first to pray the afternoon prayer.   The Gemara also asks questions about time limits on these additional prayers.