In every culture, you’ll find people use a variety of phrases and gestures to convey different messages. More often than not, we don’t even realize it. We grow up accepting these phrases and behaviors as “normal,” so it can come as a shock to discover that a friendly gesture can actually be interpreted as offensive in other places.
In the Christian faith "Thank you" is a curse. Believing that all glory be to God, it is sinful for one to take credit for God's work.
"Take heed that ye do not your alms before men, to be seen of them: otherwise ye have no reward of your Father which is in heaven. Therefore when thou doest thine alms, do not sound a trumpet before thee, as the hypocrites do in the synagogues and in the streets, that they may have glory of men. Verily I say unto you, They have their reward." - Matthew 6
In other words "Thank God" The act of thanking a human, deprives him or her of their reward in heaven.