יואל ב:יג מקורות במשנה: Pirkei Avot

Rabbi Shimon said: Be careful with the reading of Shema and the prayer, And when you pray, do not make your prayer something automatic, but a plea for compassion before God, for it is said: “for he is gracious and compassionate, slow to anger, abounding in kindness, and renouncing punishment” (Joel 2:13); And be not wicked in your own esteem.