Section 790 When the disciples left the school of R. Ammi, they used to say to him: During your life, may you see your worldly needs provided, But may your ultimate reward be in the world-to-come, And may hope for it endure through the generations that spring from you. May your heart meditate understanding, Your mouth speak wisdom, And your tongue be moved to song. May your gaze scan what lies ahead, Your eyes shine with light of Torah, Your face be radiant as the brightness of the firmament. May your lips utter knowledge, Your reins rejoice in uprightness, And your steps hurry to hear the words of the Ancient of Days.I love the reference to song, even those who study all the time should sing.
I don't understand "Your reins rejoice in uprightness,". Is the Hebrew or the original clearer or don't I just get it? What does reins refer to?