Bo: Chapter 1
"If there an angel over him, an interpreter"

Rabbi Yehuda tells us that people who study Torah and observe its commandments have an Advocate stand up for them before God rather than an Accuser, for just as there are accusers in the world below, there are adversaries above as well. Rabbi Chiya wonders why if someone keeps the commandments it is necessary to have an angel intercede for him. Rabbi Yehuda answers that it is true that God sees everything, but He gave permission to the Other Side to accuse people in this world.