Likutei Moharan 9:1/ליקוטי מוהר"ן ט׳:א׳

1“T’homot Y’chasyumu (The deeps covered them); they sank into the depths like a stone.” (Exodus 15:5)

2The essence of life-force comes from prayer, as is written (Psalms 42:9), “Prayer to the God of my life.” This is why a person should pray with all his energy. When a person prays with all his strength and concentrates his energy into the letters making up the prayers, his energy is renewed there. This corresponds to (Lamentations 3:23), “They are renewed each morning; great is Your emunah (faith).” And faith is prayer, as in (Exodus 17:2), “And his hands were emunah,” which Onkelos renders: “[his hands] were spread out in prayer.”