5. Mose (Dewarim) 32:3

כי שם ה' אקרא WHEN I SHALL CALL THE NAME OF THE LORD [ASCRIBE YE GREATNESS UNTO OUR GOD] — You see, כי is here used in the meaning of “when”, similar to (Leviticus 23:10) “When (כי) ye come into the land”. The meaning is: when I proclaim and mention the Name of the Lord, YE ASCRIBE GREATNESS TO OUR GOD and bless His name. From here they (the Rabbis) derived the law that people make the response, “Blessed be the Name of His glorious Kingdom for ever and ever", after the recital of a Benediction in the Temple (Sifrei Devarim 306:37; Berakhot 21a; Taanit 16b).

כִּ֛י שֵׁ֥ם יְהֹוָ֖ה אֶקְרָ֑א        הָב֥וּ גֹ֖דֶל לֵאלֹהֵֽינוּ׃

because I will call on the name of the Lord: ascribe greatness to our God.