Revelation 3:14-22 was the letter to the Laodicean church. Verse 15-16 says, “I know your works, that you are neither cold nor hot. So then, because you are lukewarm…” Lukewarm is a good definition for being complacent. 

Zephaniah 1:12 says that the Lord will, “…punish the men who are settled in complacency, who say in their heart…” The literal for settled is: on their lees; like the dregs of wine. The note in my Bible says that when old wine has not been poured off it becomes thick.

Jeremiah 48:11 says, “Moab has been at ease from his youth; he has settled on his dregs, and has not been emptied from vessel to vessel, nor has he gone into captivity. Therefore his taste remained in him, and his scent has not changed.”

A complacent heart is stagnant. Hebrew 3:13 says that it is, “…hardened through the deceitfulness of sin.” Thick. At ease. Not changed. The same. Mark 4:17 described it as no root in themselves. Their roots were not deep in the soil of intimate communion with the Lord~not self-feeders.