John Gill Commentary Numbers 26:1

"And it came to pass after the plague, that Jehovah spake unto Moses and unto Eleazar the son of Aaron the priest, saying," — Numbers 26:1 (ASV)

And it came to pass after the plague
Related in the preceding chapter; how long after is not certain, perhaps before the war with Midian, exhorted to in the latter part of the preceding chapter, and of which an account is given, (Numbers 31:1–54) :

that the Lord spoke to Moses ;
out of the tabernacle, or out of the cloud:

and to Eleazar the son of Aaron the priest ;
the Lord had been used to speak to Moses and to Aaron; but now Aaron being dead, and Eleazar his son succeeding him in the priesthood, is joined with Moses, and the order here given is directed to them both:

saying :
as follows.