When CJ (Djimon Hounsou) counsels Theo (Jason Patric), he paraphrases the idea that saving a life is like saving the whole world and taking a life is like destroying the whole world. This principle is found in both Hebrew and Islamic religious texts.
The final episode of the series.
The numbers 2319 can be briefly seen in the reflection of the word "PINES" shown in a neon sign with the letter N having been blacked out. This could possibly correspond to Exodus 23:19 "The first of the first fruits of your land you shall bring into the house of the lord your God".