To say Saudi Arabia hates Israel would be a grand understatement.
The two nations have no diplomatic relations. Travelers can't fly from one country to the other. Planes can't even fly through the other's airspace.
In order to travel from one nation to the other requires travelers to take what many call a "cleansing stop." Often, flyers go to Amman, Jordan, or Cairo, Egypt, before heading on. And travelers who stop in Israel before heading to Saudi Arabia often ask Israeli officials not to stamp their passports (Saudis authorities get visibly unhappy when they see the stamp). Some frequent fliers even have an extra passport so they can keep one clear of the Israeli stamp.
That's what makes President Trump's itinerary so interesting.