זוהר בראשית — דף קכג ע”א

Rabbi Shimon explains why, in the life of Sarah, the text says “year” in the singular for the hundred and the twenty, and “years” in the plural for the seven: the hundred and twenty form the whole of the upper hidden realm and the secret of unity, while the seven years separated into judgment and mercy. Rabbi Hiyya adds that Sarah’s thirty-seven years correspond to the years between Isaac’s birth and his binding, according to the numerical value of “Vayehi”; Sarah died after the binding. Rabbi Yosi then opens with “A psalm: sing to the Lord a new song” and recalls that, according to the Companions, the cows that carried the Ark sang it. The text holds that all creatures sing, but that it was the Ark upon their backs that made them sing.