The trigger is discussed and meanings are connected.
140. What is the meaning of "then" [Az; spelled Aleph Zayin]? This teaches us that it is not permissible to call Aleph alone. [It can] only [be called] through the two letters that are attached to it, which sit first in the kingdom. Together with the Aleph, they are then three. Seven of the Ten Sayings then remain, and this is the Zayin [which has the numerical value of seven]. It is also written (Exodus 15:1), "Then (Az) sang Moses and the children of Israel."
Commentary: The past few verses have all been as a prelude to a further explanation of the Ten Sephiroth. Aleph cannot be called alone because it is the superconsciousness of creation. Everything evolves from the Aleph of Creation. The Aleph Zayin of 'then' is the initiator of being. Time is introduced causing the cycles of creation to follow. By inference the three are the sephiroth of Keter, Chokmah and Binah, the primary triad upwards facing. If Aleph suggests this primary triad then Aleph combined with Zayin fulfills the rest of creation as in what follows determined by the next seven Sephiroth. 'Then' stands on the edge of fulfillment. It is the opening that allows the rest of the energy to flow through into being. It is also a signal for the mind to awaken to its fullest potential giving birth not only to ideas but also the awareness of their shaping into forms. Our entire being must be engaged.
The quality of 'then' sets the stage then for all to come exactly in the fashion that the Aleph symbolizes Keter or the crown of creation. Also we can link this 'then' Va Y'Omer elohim y'hi Or Va Y'Hi Or where the Aleph appears in Omer, Elohim, and Or as the initiator in this opening stanza for Creation's fulfillment. Go here to find the link to this verse Gen 1:3 Genesis Verse 1