תַּאֲוַ֬ת עֲנָוִ֣ים שָׁמַ֣עְתָּ יְהוָ֑ה תָּכִ֥ין לִ֝בָּ֗ם תַּקְשִׁ֥יב אָזְנֶֽךָ׃
LORD, Thou hast heard the desire of the humble: Thou wilt direct their heart, Thou wilt cause Thine ear to attend;
Tosefta Berakhot
[A person] who prays [Shmoneh Esreh] must pay attention [to the meaning of the words]. Abba Shaul says, “There is a reference for [the need of attention in] prayer [in the Tanach], ‘Prepare their hearts, pay attention.’ “ (Psalms 10:17)