What is the ruling on saying "Good morning" and "Good evening"?

We do not know of any harm in saying "good morning" after initiating the greeting and the lawful response. The greeting of Islam is "Assalamu Alaikum," and if "wa Rahmatullah wa Barakatuhu" is added, it is better. If "good morning" is invoked after that, there is no harm. However, restricting oneself to it without the greeting is an offense.