In a letter to Spicer shared with the media on Thursday, ADL CEO Jonathan Greenblatt said his organization “would be happy to conduct one of these trainings at your convenience for you, your staff, and anyone at the White House who may need to learn more about the Holocaust. We know you are very busy, but we believe a few hours learning this history will help you understand where you went wrong and prevent you from making these mistakes in the future.”

In a media briefing Tuesday, Spicer compared the Syrian government’s role in a chemical weapons attack that killed at least 87 Syrians to the tactics of the Nazi regime.

“We had someone as despicable as Hitler who didn’t even sink to using chemical weapons,” Spicer said.

Pressed by Jewish groups and others who noted that the Nazis regularly used poison gas to kill Jews in concentration camps, Spicer later apologized, saying he made “an inappropriate and insensitive reference to the Holocaust, for which frankly there is no comparison.”

In the ADL’s letter to Spicer, Greenblatt noted that the press secretary made his original remarks on the first day of Passover.

“Unfortunately, when the first days of Passover ended and we turned on our phones and televisions yesterday evening, we learned about your ignorance of the Jewish people’s history,” he wrote. “Your comparisons between Assad and Hitler were not only wrong and misguided, but they also were insulting and hurtful.”

The ADL offers training in Holocaust awareness and tolerance to law enforcement professionals and educators.

“Each of these educational programs implores participants to remember the consequences of hate left unchecked,” its letter explained.

In January, Jewish groups and others criticized the White House for omitting any mention of Hitler’s Jewish victims in a statement marking International Holocaust Remembrance Day.