Even though the recital of Keriat Shema and its berachot, and the recital of the Amidah prayer are two separate mitzvot, one must connect them, and it is forbidden to interrupt between them. The Chachamim state that anyone who adjoins redemption to prayer merits life in the World to Come (Berachot 4b). If he adjoins them while praying vatikin, he is promised that he will not be harmed that whole day (Berachot 9b, and Tosafot there). One who interrupts between redemption and prayer is considered similar to a king’s beloved, who comes and knocks on the king’s door. When the king emerges to find out what his beloved desires, he has already left to take care of another matter. The mention of Israel’s redemption from Egypt is akin to the knock on the king’s door, because the redemption demonstrates the great love HaKadosh Baruch Hu has for Israel. Therefore, the Exodus from Egypt is considered as the engagement between HaKadosh Baruch Hu and Israel. Distractions are forbidden. Out of the special closeness expressed in the redemption, we must maintain the state of devotion sparked by prayer and request that Hashem bless and redeem us, just as He redeemed us from Egypt (see Yerushalmi Berachot chapter 1, halachah 1).
Even if a person hears Kaddish or Kedushah between redemption and prayer, he may not answer (Shulchan Aruch 66:9). One may not interrupt at all, even silently, between redemption and prayer.
Many chazanim are accustomed to concluding Birkat Ga’al Yisrael quietly so that people will not answer Amen. The reason for this is that some say that one who finished Birkat Ga’al Yisrael, but did not yet start the Amidah, and heard the chazan’s conclusion of Ga’al Yisrael must answer Amen. They maintain that it is not considered to be an interruption (hefsek), since answering Amen to Ga’al Yisrael is a continuation of one’s involvement in redemption (Rama). However, others maintain that even answering Amen to Birkat Ga’al Yisrael constitutes an interruption between redemption and prayer (Shulchan Aruch). Therefore, in order to spare the congregation from uncertainty, some chazanim conclude the berachah silently, so that no one can answer Amen. Others are less concerned and conclude Birkat Ga’al Yisrael in a regular voice. At a time when there were people in the congregation who fulfilled their obligation by hearing the chazan, the chazan was required to recite the whole berachah out loud.
One who arrives late, when the congregation is about to begin the Amidah, must recite the prayers in the correct order and adjoin redemption to prayer. Despite the fact that he will miss praying with the congregation, it is preferable that he prays in the proper order, since the adjoining of redemption to prayer is preferable to prayer in a minyan. However, concerning Ma’ariv, the law is different (Shulchan Aruch 236:3; and see further in this book 25:4).
According to the majority of poskim, on Shabbat it is less necessary to adjoin redemption to prayer. Therefore if one hears Kaddish or Kedushah between redemption and prayer, he should respond to it.
If he must hear the Kaddish and Kedushah because he will not have another opportunity to respond to them, he should practice according to the Shulchan Aruch 66:9; waiting at the words “Shirah chadashah” and answering. Regarding one who was brought tallit and tefillin in the middle of Birkat Ga’al Yisrael, see end of note4 in this chapter.
. The Shulchan Aruch 111:1, based on the Zohar, rules that an Amen recited after the Ga’al Yisrael berachah is considered to be an interruption, although according to the Tur and the Rama it is not. Nevertheless, the Mishnah Berurah 66:35 writes that it is good to refrain from putting oneself in a position of uncertainty by concluding the berachah of Ga’al Yisrael together with the chazan. It is best that one who finishes before him already starts saying the words, “Hashem sefatai tiftach….” In that way, even according to the Rama he will not need to say Amen. The Aruch HaShulchan (who lived in Ashkenaz) 111:2 writes that in any case, even if he did not start the Amidah, the custom is not to answer Amen. Concerning the minhag to finish Ga’al Yisrael quietly, see Beit Baruch 20:56 who expresses doubt concerning this. However, there are others who praise the custom; see Ishei Yisrael 17 note 83.