Exodus 15:23
They came to Marah, but they could not drink the water at Marah because it was bitter—that is why it was named Marah.
Numbers 33:8
                            
Ruth 1:20
                            “Don’t call me Naomi. Call me Mara,”
Treasury of Scripture Knowledge
Summary
                            And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah.                        
                    Marah
Bible References
Marah
                                        Numbers 33:8                                        They departed from Pi-hahiroth and crossed through the middle of the sea into the wilderness. They took a three-day journey into the Wilderness of Etham and camped at Marah.  
 
                                    
                                                                                                                                
                                        Ruth 1:20                                        
                                                            
                        “Don’t call me Naomi. Call me Mara,” she answered, “for the Almighty has made me very bitter.