Why Moses Opened the Song at the Sea with the Word Az

"Then sang Moses" (Exodus 15:1). Why did Moses our teacher, peace be upon him, begin the Song with "Then" (az)? Moses our teacher, peace be upon him, said: I transgressed with "then," as it is written, "And from then (u-me-az) I came to Pharaoh to speak in Your name" (Exodus 5:23); and so I will make amends with "then," and he opened the Song with "then." Another interpretation: Why did Moses open with "then"? Because from the dry land He made sea with "then," as it is written, "Then (az) was it begun to call upon the name of the Lord" (Genesis 4:26), and concerning them Scripture says, "He who calls to the waters of the sea and pours them out upon the face of the earth" (Amos 5:8); therefore I praise Him [with "then"] at the sea. Another interpretation: "Then" (az) — what is the numerical value of "az"? It is eight. This teaches you that Israel was redeemed only by the merit of the circumcision, which was given for the eighth day. Another interpretation: Moses said: With "then" the circumcision was given, and my life was given to me, as it is said, "Then (az) she said, A bridegroom of blood for the circumcision" (Exodus 4:26). Another interpretation: "Then" (az) — for the sake of the Only One of the world, who is One above the seven firmaments.