The Laws of Prayer [i.e. the Amidah] and its [Proper] Time, containing 8 s'ifim
The time for the morning Tefillah (i.e. Amidah): its commandment is that it should begin with the "blossoming" (i.e. rising) of the sun, as it is written, "They will revere You with the sun (Psalm 72:5)." And if one prayed from the [time of] "the pillar of the morning" (i.e. dawn) and the appearance of the east has become light, one has fulfilled [one's obligation]. And its time continues until the end of four hours which is a third of the daytime. And if one erred or transgressed and prayed after the fourth hour until noon, even though one does not have the [same] reward as praying at its [proper] time, in any case there is still a reward of prayer. Rem"a: And after noon it is forbidden to pray the Tefillah of the morning (Beit Yosef in the name of the Rashba [Rabbi Shlomo ben Adret], Chapter: "Morning Prayer") . And see below, the beginning of Siman 108].
When the time of prayer has arrived, it is forbidden for a person to arrive early to the door of one's friend to greet him (lit. "give them a 'shalom'"), since the name of the Holy Blessed One is "Shalom", but it is permitted to say to him, "Good morning, sir" (tzafra d'mari tav). And even this is not allowed other than when it is needed to go to see to a matter of business, but if one is only going to greet (i.e. for a purely social purpose) before prayer, even this phrase is forbidden. And it is also forbidden to bow to them [in greeting] when one gets up early to go to his door (ie. before praying). And there are those that say that bowing is forbidden even when you do not get up early to go to his door. And if one has begun to bless the [morning] blessings (after this) there is no concern with any of this. And if one does not get up early to go to his door, but rather encounters him on the way, it is permitted to greet him (give them a "shalom"). And there are those that say that even if one finds one's friend in the marketplace, one should not say to him anything other than "Good morning, sir", since this reminds (lit. "gives heart") [him] that it is forbidden to to delay with other matters until one prays.
It is forbidden to busy one's self with his own needs or to get on the road before praying the prayer of 18 [i.e. the Amidah] (and there are those who are lenient [to allow this] after they have said some of the blessings before saying Baruch She-amar, but is good to be stringent in this - Terumat HaDeshen 18) nor may one eat or drink, but one may drink water before prayer, both on a weekday and on Shabbat or Yom Tov, and likewise, foods or drinks for medicinal purpose is allowed.
One who is thirsty and one who is hungry - behold they are in the category of the ill. If one has the ability to focus one's mind, one should pray. If not, if one wishes, one should not pray until eating or drinking.
If one began to eat before dawn, one must stop. And there are those that say one does not need to stop.
Even to learn is forbidden once the time for prayer has arrived. And this is regarding one who normally prays in his house of study and does not normally go to synagogue, as there is reason to be concerned that he will become absorbed in his learning and the time of the Recitiation of Sh'ma and of prayer [i.e. the Amidah] will pass. But [for] one who normally goes to synagogue [to pray] - it is permitted. And if one is [in the middle of] teaching others, even if he does not normally go to the synagogue [to pray], it is permitted [to continue learning] since the time will pass, for [teaching Torah to others which is] a benefit to the people is a great matter, and if they do not learn now, they will sit idly and they will not be able to learn.
It is permitted to get a hair cut and to enter the bathhouse close to the time of Shacharit since they (ie. the Sages) only decreed [to not do those things] close to the time of Mincha since it is common [for people to do those things in the afternoon].
In an extenuating circumstance, for example, if one needs to get up early for a journey, he may pray [the Amidah] at dawn, and wait to recite the Sh'ma until the proper time has arrived [if it is possible for one to recite the Sh'ma on the journey, that is, if one will be able to have proper concentration for the first verse , as was explained above in Siman 58.] (Beit Yosef in the name of the Rashb"a). And even though [by doing this] one is not adjoining [the blessing of] redemption [that immediately precedes the Amidah] to the [Amidah] prayer it is still better to pray in one's house while standing (ie. with proper concentration) than praying at its proper time while going [on the road] and [being able to] adjoin redemption to the prayer.