For years growing up, during the month of Ramadan, Muslims would greet each other with As Salaam Alaikum and Ramadan Mubarak. The response would be Walaikum as Salaam and Ramadan Kareem. Some years back when Imam W.D. Mohammed was still alive, he gave a talk about the difference between the two. I did not hear it firsthand but I think it was brought up during a Jumah khutbah, and my dad (who did hear it firsthand) relayed it to me. According to my dad, the Imam said that he did some extensive research on the life and practices of Prophet Muhammad PBUH and his companions, and while there was plenty of evidence of use of Ramadan Mubarak, he could find absolutely nothing on the use of the phrase Ramadan Kareem. The Imam concluded that maybe the Arabs, who did not have the same respect for other (western) Muslims, came up with the phrase to address them. Amongst themselves, they greet each other with Ramadan Mubarak, but to other foreigners, their greeting would be Ramadan Kareem. Though several older Muslims bear witness to hearing the Imam explain it, nobody can pinpoint which lecture/speech he said it in. I would like to hear it for myself, so Inshallah someone will find it. Google didnt help much either since many of the Imams lectures arent indexed for searching. I did find the following explanation that is somewhat kinda sorta along the same lines.
"Again, we wish everyone Ramadan Mubarak which means, “Blessed Ramadan”. And the most appropriate response to Ramadan Mubarak is Ramadan Mubarak. Now, I know that we have gotten used to saying Ramadan Kareem and Ramadan Sayeed. However, Allah says that when a greeting is given to you, you should reply with a greeting more excellent or at least it’s equal. So, if I say Ramadan Mubarak and you say Ramadan Kareem, you’re giving me less than what I gave you. As predominantly Muslim African Americans, we have to begin taking serious measures towards learning the accuracy in the Qur’anic language or else people will come along and introduce ideas into the religion that are actually foreign to the letter and spirit of the Qur’an and what El Islam represents.
In the Qur’an Allah says that, Ramadan is the month that is full of blessings or “mubaraka”. That’s what Allah says. So, to say “Ramadan Mubarak” is right in line with what Allah says about Ramadan in the Qur’an itself. But nowhere in the Qur’an will you find these other appendages. Therefore, if I’m giving you something that is from the Qur’an and you are giving me something in return that is from some other source, you’re giving me less than what I gave you. That does not represent obedience to the letter or spirit of the Qur’an."
Since the Imam told us to stop using Ramadan Kareem, I've seen it used less but still see it used by some. Im not here to tell anyone how to be a Muslim or what is right or wrong in their actions. I wanted to know this information for myself and share with anyone who is interested.