4:24 This is the service of the families of Gershonites, as they serve 1 and carry it.
Numbers 7:7
7:7 He gave two carts and four oxen to the Gershonites, as their service required;
1 tn The two forms are the infinitive construct and then the noun: “to serve and for the burden.” They are to serve and they are to take the responsibility. The infinitive is explaining the verb.