The Holy Trinity of Weed is the three basic things one might have while smoking. Weed, A lighter & Visine or other eyedrops. If you have those three, you can pretty much smoke anywhere with anything (pipe, blunt, bong etc) And the eye drops are for stopping redness in the eyes. Mostly in backpacks of high school students.
Jim: Bro, I wanna smoke before class/
Joe: We should throw fives. But how are we gonna get it fast?
Jim: Its cool. Marks got the Holy Trinity in his backpack.