The verse "Yahweh spoke to Moses, saying," from Numbers 16:44 is a common formulaic introduction to a divine command or instruction given by God (Yahweh) to Moses. Let's break down its significance:

Yahweh: This is the personal name of God in the Hebrew Bible. It emphasizes the direct and personal connection between God and Moses.

Spoke: This indicates a direct verbal communication from God. It suggests that God is not a distant or abstract being but actively communicates with humans, in this case, Moses.

To Moses: Moses is identified as the recipient of this divine communication. This reinforces his role as the primary prophet and mediator between God and the Israelites.

Saying: This word signals that what follows is a direct quotation of God's words or instructions. It emphasizes the authority and importance of the message.

In the context of Numbers 16:44: This verse appears after a rebellion led by Korah, Dathan, and Abiram, which resulted in a plague breaking out among the Israelites. God's speaking to Moses at this point likely indicates that He is about to give instructions on how to stop the plague and reaffirm His chosen leadership through Moses and Aaron. It is a moment of divine intervention in the midst of a crisis, where God is taking direct action to address the situation.

In summary, the verse "Yahweh spoke to Moses, saying," serves as a literary device to:

Emphasize the divine origin of the following message.
Establish the authority of Moses as God's chosen messenger.
Indicate a direct and personal communication from God.
Highlight the importance of the forthcoming instruction.