Numbers 31:29-31 commands giving a portion to Eleazar; this verse records Moses actually giving it, fulfilling the command.

Numbers 18:8 establishes the priestly portion from contributions; this verse is a concrete instance of that law applied to war tribute.

Numbers 18:19 establishes the perpetual due of holy contributions to priests—this tribute to Eleazar is a direct application of that covenant.

In 1 Corinthians 9:10-14, Paul argues from OT priestly support (like this tribute) that gospel workers deserve material support.

Exodus 29:28 commands a perpetual due for Aaron's sons from peace offerings—this tribute is an example of that command.