Tosefta zu Nechemja 9:5

[The people] do not answer Amen in the Bet Hamikdash (Temple) [after Berachot, but rather say instead Baruch Shem Kevod Malchuto Leolam Vaed (Blessed be His glorious Name forever and ever)]. And from where [do we know] that they do not answer Amen in the Bet Hamikdash? As it is said, “Get up, bless Hashem, your God, from the world until the world.” (Nehemiah 9:5) And it says, “And let them bless Your glorious name.” (ibid.) And from where [do we know that] for every single blessing and for every single praise [and not just at the conclusion of all blessings of Shemoneh Esreh, they say instead of Amen, Baruch Shem Kevod Malchuto Leolam Vaed]? The verse teaches us, “… and exalted beyond every blessing and praise.” (ibid.) [Meaning] for every single blessing and for every single praise [they say Baruch Shem Kevod Malchuto Leolam Vaed].