tending to indulge in pompous moralizing.

In a sentence:
Professor Leibowitz was very popular with his students, who enjoyed her sententious lectures; not because they were any good, but because they were over very quickly.

In a different sentence:
Harry’s friends resented his sententious style of speaking; they constantly felt like they were actually being lectured by a high school dropout with 3 STDs. What a hypocrite!

A joke:
What did the sententious dictator say to his people?
“Freedom! Democracy! Stay the course! Bring it on!”

Fact:
Jimmy Swaggart’s sententious proclamations curiously evolved into a simple “God says it’s none of your business!” when he was caught with a series of prostitutes in the late 1980s.