Haggai, chapters 1 & 2

“[…] That is how all the work of their hands is; whatever they present there is unclean.”
~Haggai 2:14

God doesn’t care so much about the sacrifice we are giving him as he does about what motivates us to give it. (Hag. 1:5)
We should not undermine our privilege of knowing and serving the true God by letting our worship become mechanical and superficial in nature.
Those who try to serve God hypocritically lose his blessing and his friendship.
On the other hand, if we ‘set our heart in our ways’ by trying to find joy in his service, we can experience more blessings than we could have imagined. (Hag. 2:7; Mal. 3:10)