Fixing a place for prayer

The Gemara from Berakhot 6a to 8a has a number of statements about the importance of a synagogue. Some samples from 6a–b, with Soncino translations:

תניא אבא בנימין אומר אין תפלה של אדם נשמעת אלא בבית הכנסת שנאמר (מלכים א ח) לשמוע אל הרנה ואל התפלה במקום רנה שם תהא תפלה 

It has been taught: Abba Benjamin says: A man's prayer is heard [by God] only in the Synagogue. For it is said: To hearken unto the song and to the prayer. The prayer is to be recited where there is song.

אמר רבין בר רב אדא א"ר יצחק מנין שהקב"ה מצוי בבית הכנסת שנאמר (תהילים פב) אלהים נצב בעדת אל

Rabin b. R. Adda says in the name of R. Isaac: How do you know that the Holy One, blessed be He, is to be found in the Synagogue? For it is said: God standeth in the congregation of God.

Ge’ullah and tefillah

The first half of Masekhet Berakhot covers two main topics, the Shema with its blessings and the Amidah. One subject arises multiple times as a glue that joins the two topics together (five times, to be exact, according to the Bar Ilan Responsa Project: on 4b, 9b, 10b, 26a, and 30a). This is the requirement to be somekh ge’ullah li-tfillah—that we connect the redemption at the end of the Shema’s blessings, “ge’ullah,” to the start of the Amidah, “tefillah.” The Halakhah gives this requirement high priority.

What is the reason for semikhat ge’ullah li-tfillah? And why is it so important?