Isaiah 1:19-20 If ye be willing and obedient, ye shall eat the good of the land: But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the LORD hath spoken it.

Before this verse the Lord tells how the Israelites sacrifices, sabbaths, religious holidays and gatherings were all empty and made the Lord "weary".  They were still living sinful loves -- yes they kept most of the outward "rituals" but they were empty.  Their hearts weren't right with God, and God doesn't want our sacrifice, he wants our hearts.  vs 19 says "willing and obedient", it starts with a willing heart and the result of a willing heart is a life obedient to God.

May our church services, prayer meetings and Bible study not make God "weary" but be a reflection of what is truly in our heart.  May we not "refuse and rebel" lest judgment come.