What does the Bible say about speaking against God's servants?

In Numbers 12, Miriam and Aaron spoke against Moses, expressing dissatisfaction over his marriage to a Cushite woman. The Lord heard their words and summoned them to the tabernacle, making it clear that speaking against His servant was a grave offense. God emphasized the unique relationship He had with Moses, stating, 'Not so my servant Moses.' This incident illustrates the seriousness of undermining God's appointed leaders, not to be confused with proper rebuke for sin. Instead, it teaches us to respect those whom God chooses to lead.