The proverbial expression of the mills of God grinding slowly refers to the notion of slow but certain ‘divine retribution’. 

There are a lot of references to this phrase by several popular littérateurs; Arthur Conon Doyle, Agatha Christie, Somerset Maugham and well known leaders like Winston Churchill and Franklin Roosevelt. 

In Tamizh also there is a corresponding adage which goes like ‘Deivam Nindru Kollum’ (meaning the God’s punishment would be slow’).

But, in my fairly long life, I have not seen much of this ‘divine retribution’ slowly or otherwise. 

A very senior person in my profession was positively full of hubris. He wasn’t countered by many for long. He was positively arrogant and aggressive with no commendable credentials. In the later part of his life, he was just ignored by all. This is a very miniscule example I could recall as far as saying is concerned. In public life if one looks, we need to doubt whether such a statement is honestly valid or carries any meaning or sense. 

I personally feel that there are no retributions for anyone or anything. Everyone gets their share and more or less according to their ‘destiny’. The Hindu philosophy conveniently says that everyone reaps the good or bad ‘according’ to their ‘sins’ or ‘good deeds’ they have done in their previous birth. So there are no further proof or questions or discussion. 

A ’retribution’ or ‘punishment’ becomes valid only if the person feels or realizes it as one. A man after committing numerous heinous crimes walking into the prison or gallows with nonchalance cannot be termed as retribution.  

I have no idea if there is any axiom for that.