amen to that

Examples from literature

"Amen," replied both the guests. 
"Amen," said Margaret with white lips. 
Each week we wrote two sermons and a lecture all out, from the text to the amen. 
In the name of the bee And of the butterfly And of the breeze, amen! 
Thus God provides for his creatures, unto whom be praise, now and for ever more, amen. 

amen | American Dictionary

amen
exclamation, noun[ C ]
us/ɑˈmen, eɪ-/
(said or sung at the end of some prayers or religious songs) it is so
You can say amen to show that you agree strongly with something that someone has just said:
“Two public service announcements will address the habit of running red lights.” “Amen to that!”