Argh, I posted a thread about it earlier, but I'm in a game with Venice, and I decided to go for a religion when I saw that a nearby city state was 2 tiles away from Mount Sinai (+8 faith). Unfortunately, when I got the city state, I realized I couldn't buy tiles, and then the city state had no culture so no border expansion, then when I bought a monument, I soon researched animal husbandry, and they changed their expansion towards some horses 3 tiles away from the city! The mountain finally came within my borders 200 years after the last religion was founded (325 BC), and Venice didn't become religious until 1300 AD... Really annoying...