Numbers 14:36

And the men, which Moses sent to search the land, who returned, and made all the congregation to murmur against him, by bringing up a slander upon the land,

Cross-references

Numbers 13:31-33 records the spies' bad report that caused the grumbling, the event directly referenced here.

Numbers 13:32 records the evil report the spies brought—the 'slander' referenced in 14:36 that sparked the congregation's rebellion.