It's called, "We Haven't Missed a Sabbath Yet," and sets to subject matter of the show wonderfully. The problem for director Jerome Robbins is that it didn't set the theme of the evening. So for a long while, the creators would get together and discuss what the show as about. After a while, someone mentioned that it was about the loss of traditions as life progressed and some of the past got left behind. That's what Robbins was looking for. And Harnick and Bock went back and worked out a new song. It, of course, became the iconic, "Tradition."
Most of the original song was jettisoned, but if you listen closely you'll still hear a few music themes that got retained from the first effort.
By the way, I should mention that these songs are from a wonderful 2-CD compilation called, Sheldon Harnick: Hidden Treasures, 1949-2013. You can find it here on Amazon.
Here's that lost opening song sung by the composers.