Drinking Custom

Why Do People Say "L'chaim" When Drinking?

Shalom! 

Thank you for your question. 

The original source for saying Le'chaim is brought by Rashi Mesechet Shabbos (page 67b) 

Some say that the reason for this is that wine and other alcoholic drinks were provided to criminals immediately prior to their execution in Biblical and Talmudic times in order to lessen their suffering. Therefore, saying l’chaim declares to everyone present that the function of this drink is intended as a celebration of life and not as a preparation for death, G-d forbid. 

Another reason is that we are told that Adam became drunk from the wine he drank at his wedding ceremony, which led to him and Eve eating the forbidden fruit. Indeed, there is a view that the forbidden fruit was a grape which Adam and Eve made into wine. This brought death to the world forever. Saying “l’chaim” is intended to recall and rectify this. Similarly, wine led to the downfall of Noah, so we say “L’chaim” to symbolize that we want no harm to come from our drinking. There are other reasons, as well. 

Some have the custom is to say “l’chaim” before reciting the blessing on wine (or other alcoholic drink) some say it after reciting the blessing and first drinking a little bit. One should respond “l’chaim tovim u’lshalom” or “l’chaim u’livracha” when hearing someone say “l’chaim.” 

It is noted that we say “L’chaim” which means “to lives,” in the plural. This is intended to remind us that a meaningful life is one that is shared with others.

 Berachot 40a; Sanhedrin 70a; Daat Zkeinim, Shemini 10:9; Mateh Moshe 349; Kaf Hachaim, OC 167:108; Taamei Haminhagim p. 496;