Kissing the Mezuza
It is actually somewhat unclear where the widespread practice to kiss the mezuza when entering or exiting a room originates from. It is not directly mentioned in any early rabbinic texts.[1] Nevertheless, a number of explanations for the custom have evolved throughout the ages.
One possibility is that the practice derives from an inspiring incident in the Talmud regarding Onkelos, the famous convert to Judaism and author of the "Targum Onkelos" translation of the Torah. The Talmud records that following Onkelos' conversion to Judaism, the Roman emperor tried to have him arrested and returned to his service. Upon the arrival of the emperor's soldiers to his home, Onkelos shared with them some beautiful Torah thoughts and teachings which inspired them to convert on the spot. Again soldiers were sent to try and retrieve Onkelos from his newly adopted lifestyle, but they too were won over by Onkelos' infectious love for Judaism and they converted, as well. Soldiers were dispatched yet a third time but this time the soldiers were instructed not to allow Onkelos to even speak when arresting him or engage him in any conversation. And so they did. When they were leading him away, however, Onkelos placed his hand on the mezuza and remarked that "Normally, a human king sits inside and his servants stand outside and guard him. But with the Holy One Blessed be He, His servants are inside and He guards them from outside." With that, they too converted. The emperor then ceased sending soldiers.[2]
Based on the precedent of Onkelos[3] the Rema writes: "Some say that when one leaves one's home, one should place one's hand upon the Mezuza and recite the verse "God will guard my coming and going from now and forever". So too, when one enters one's home one should place one's hand on the Mezuza, as well."[4] Some authorities suggest reciting a number of additional verses which discuss Divine protection when leaving one's home.[5] There is no mention of kissing the mezuza anywhere in the related codes or commentaries.
It appears that the first mention of kissing a mezuza dates to the 1500's and originates with the Arizal. It is written in the name of the Arizal that: "One should put his finger on the word Shadd-ai which appears on the mezuza and then kiss it and pray that God save one from the Yetzer Hara."[6] In addition to being one of God's names, the word Shaddai which appears on the back of every mezuza is an acronym for "shomer diras yisrael"[7], Guardian of Jewish dwellings, or alternatively, "shomer daltot yisrael",[8] Guardian of Jewish doors. Many authorities encourage one to kiss one's hand after touching other ritual articles as well, such as Tefillin or a Torah scroll.[9] Indeed, kissing religious articles is an often cited means for expressing one's love and affection for mitzvot.
It is also noted that one of the purposes of the mezuza is to remind a person of the unity of God and to arouse a feeling of love for Him.[10] It might just be that the custom of kissing the mezuza was instituted in order to force a person to pause for a moment in order to ponder these thoughts.[11] Some authorities frown upon the practice of merely kissing one's hand as a sign of affection when touching ritual objects and argue that only kissing the object directly can serve this purpose.[12]
It is interesting to note that the Kitzur Shulchan Aruch in Chapter 11 writes that the Mezuza should be kissed when entering and exiting one's home. However, in Chapter 71 when discussing the custom of touching the mezuza before going to bed each night, the notion of kissing the mezuza is mysteriously absent. It merely says that one should place one's hand on the mezuza before going to bed. As such, it might just be that kissing the mezuza is only of significance when entering and exiting a room or building but not when touching it at other times.
[1] Shu"t Rabbi Akiva Eiger 58.
[2] Avoda Zara 11a; Be'er Moshe 2:98.
[3] Biur Hagra, YD 285:5.
[4] Rema, YD 285:1; Chayei Halevi 2:66:7.
[5] Darkei Moshe, YD 285; Shach, YD 285:4.
[6] Birkei Yosef, YD 285:4.
[7] Darkei Moshe, YD 288:3.
[8] Siddur Ha'arizal; Zohar, Va'etchanan p.266b.
[9] Ben Ish Chai, Vayera.
[10] Rambam, Hilchot Mezuza 6:13.
[11] Kitzur Shulchan Aruch 11:24.
[12] Zecher Natan, cited in Bishvilei Haparasha p.518.