Ismar Elbogen, Jewish Liturgy. 1913.
(excerpt from 1993 edition, translated from the German by Raymond P. Scheindlin)
The structure of the Amidah – hymnic introduction, petitions, and thanksgiving – clearly goes back to biblical models, and therefore cannot have originated very long after the biblical period. The contents of the petitions were originally very general. Like the petitions in the late biblical books, they seem to have taken as a starting point the sinfulness of man; and the material things for which worshipers prayed were only such as were indispensable to everyone, and therefore equally dear to the hearts of all members of the community. To these belonged also several wishes of the community as a whole, such as the petition for Jerusalem and the Temple, and, rather early, as we learn from the Apocrypha, for the uniting of all of Israel's scattered people. Late biblical and apocryphal prayers explain the practice of introducing the prayers by referring to the covenant between God and the ancestors. This testifies to a firm and self-assured faith in the continuing protection and favor of God, a faith that the later generations did not always share. The confession of sin also flows from a perfectly sound consciousness, and is free of the masochistic self-reproaches of the period before the destruction of the state [Jerusalem].
Jewish Virtual Library: The Amidah
In the 5th century B.C.E., the 120 men of the Great Assembly composed the basic text of the Amidah. The exact form and order of the blessings were codified after the destruction of the Second Temple in the first century C.E. The Amidah was expanded from eighteen to nineteen blessings in the 2nd century C.E., under the leadership of Rabbi Gamliel the Elder in Yavneh. The additional blessing (against heretics) was initially meant to combat the threats posed by the Samaritan and Sadducee sects, and was permanently added to the liturgy when Jewish converts to Christianity began to inform on Jews to the Roman authorities.English
(ב) בָּרוּךְ אַתָּה ה' אֱלהֵינוּ וֵאלהֵי אֲבותֵינוּ. אֱלהֵי אַבְרָהָם. אֱלהֵי יִצְחָק. וֵאלהֵי יַעֲקב. הָאֵל הַגָּדול הַגִּבּור וְהַנּורָא אֵל עֶלְיון. גּומֵל חֲסָדִים טובִים. וְקונֵה הַכּל. וְזוכֵר חַסְדֵּי אָבות. וּמֵבִיא גואֵל לִבְנֵי בְנֵיהֶם לְמַעַן שְׁמו בְּאַהֲבָה:(ד) מֶלֶךְ עוזֵר וּמושִׁיעַ וּמָגֵן: בָּרוּךְ אַתָּה ה', מָגֵן אַבְרָהָם:
(2) Blessed are You, Lord our God and God of our fathers, God of Abraham, God of Isaac and God of Jacob; the great, mighty and awesome God, the most high God, Who bestows loving kindness and goodness and is master/creator of all, Who remembers the good deeds of the fathers, and brings a redeemer to their children, in love and for the sake of His name. (4) King, Helper, Savior, and Shield. Blessed are You, O Lord, Shield of Abraham.
(א) אַתָּה גִּבּור לְעולָם אֲדנָי. מְחַיֵּה מֵתִים אַתָּה רַב לְהושִׁיעַ: (ד) מְכַלְכֵּל חַיִּים בְּחֶסֶד. מְחַיֶּה מֵתִים בְּרַחֲמִים רַבִּים. סומֵךְ נופְלִים. וְרופֵא חולִים וּמַתִּיר אֲסוּרִים. וּמְקַיֵּם אֱמוּנָתו לִישֵׁנֵי עָפָר. מִי כָמוךָ בַּעַל גְּבוּרות וּמִי דומֶה לָּךְ. מֶלֶךְ מֵמִית וּמְחַיֶּה וּמַצְמִיחַ יְשׁוּעָה: (ו) וְנֶאֱמָן אַתָּה לְהַחֲיות מֵתִים: בָּרוּךְ אַתָּה ה', מְחַיֵּה הַמֵּתִים:
(1) You are mighty forever, O Lord, You revive the dead, You are mighty to save. You sustain the living with loving kindness, You revive the dead to life with great mercy, You support the fallen and You heal the sick; You free the captives and preserve Your faith with those asleep in the dust. Who is like You, Master of mighty deeds? Who can be compared to You, O King Who causes death and restores life, and causes Your salvation to sprout.
You are faithful to restore the dead to life. Blessed are You, O Lord, Who brings life to the dead.
(א) אַתָּה קָדושׁ וְשִׁמְךָ קָדושׁ וּקְדושִׁים בְּכָל יום יְהַלְּלוּךָ סֶּלָה: בָּרוּךְ אַתָּה ה', הָאֵל בעשי”ת: הַמֶּלֶךְ הַקָּדושׁ:
(1) You are holy and Your Name is holy, and holy ones praise Your name every day. Blessed are You, O Lord, the holy God. (During the Days of Awe say: Blessed are You, O Lord, the holy King.)
(ג) רַבָּן גַּמְלִיאֵל אוֹמֵר, בְּכָל יוֹם מִתְפַּלֵּל אָדָם שְׁמֹנֶה עֶשְׂרֵה. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, מֵעֵין שְׁמֹנֶה עֶשְׂרֵה. רַבִּי עֲקִיבָא אוֹמֵר, אִם שְׁגוּרָה תְפִלָּתוֹ בְּפִיו, יִתְפַּלֵּל שְׁמֹנֶה עֶשְׂרֵה. וְאִם לָאו, מֵעֵין שְׁמֹנֶה עֶשְׂרֵה:
(3) Rabban Gamliel says: Every day a person must pray eighteen [blessings of Shemoneh Esrei]. Rabbi Yehoshua says: [One may say] an abbreviated [form of the] eighteen [blessings]. Rabbi Akiva says: If his prayer is fluent in his mouth, he must say eighteen; and if it is not -- an abbreviated eighteen.
§ The baraita cited previously taught that the halakha against reciting a text out of order applies to the Amida prayer as well. The Gemara asks: From where do we derive this? As it is taught in a baraita: Shimon HaPakuli arranged the eighteen blessings of the Amida prayer before Rabban Gamliel in their fixed order in Yavne, which indicates that there is a specific order to these blessings that must not be changed. Rabbi Yoḥanan said, and some say that it was taught in a baraita: A hundred and twenty Elders, i.e., the Men of the Great Assembly, and among them several prophets, established the eighteen blessings of the Amida in their fixed order, which also shows that the order of these blessings may not be changed.
Rav Yehuda said: There is an additional distinction between the various sections of the Amida prayer: One must never request his own needs in the first three or in the last three blessings; rather, he should do so in the middle blessings. As Rabbi Ḥanina said: During the first three blessings, he is like a servant who arranges praise before his master; during the middle blessings, he is like a servant who requests a reward from his master; during the final three blessings, one is like a servant who already received a reward from his master and is taking his leave and departing.