The morning prayer was instituted by Abraham, as it is written (Genesis 19:27): "And Abraham arose early in the morning, to the place where he stood before the Face of G-d"... Isaac instituted the afternoon prayer, as it is written (Genesis 24:63): "And Isaac went out to meditate in the field towards evening"... Jacob instituted the evening prayer, as it is written (Genesis 28:11): "And he encountered the Place... for the sun had set."