Three Steps Forward
“When one stands up before beginning the Shemoneh Esrei, he should take three steps forward, as one would do when approaching something he needs to do. (Shulchan Aruch Orach Chaim 95:1 — Rema in the name of the Rokeach)
According to the Rokeach the custom corresponds to three occasions that the Torah mentions “approaching” in connection to prayer; by Avraham, Yitzchak and Eliyahu. Though the Rema mentions only three steps forward, the prevalent custom today is to first take three steps backward before taking three steps forward (Kitzur Shulchan Aruch; Mishnah Berurah; Kaf Hachaim and others).
The Kitzur Shelah explains that the correct understanding of the Rokeach is to take three steps backward in order to take three steps forward. He explains that these three steps forward are connected with the three steps Moshe took when approaching
In the sefer Chut HaShani (54), as well as in the Ben Ish Chai (Parshat Beshelach, Halacha 3), another reason is offered for the three steps backward and forward. They parallel the distance of three “mil” (approximately three kilometers) that the Jewish People were forced backwards at Mount Sinai, followed by a three mil forward movement. The Ben Ish Chai adds that according to Kabbalah one is obligated to take these three steps. The Yalkut Yosef states that, strictly speaking, one is not obligated to take these three steps. Perhaps his reason is due to the Shulchan Aruch's not including this rule in his laws of prayer.
The Kitzur Shulchan Aruch explains the above procedure in detail. He writes: Before Saying “Tehillot La’E-l Elyon” (found just before the conclusion of the blessing before the Shemoneh Esrei), you should stand (this was also the custom of the Arizal) and prepare yourself to pray… and then walk backward three steps and say: “Tehillat La’E-l Elyon”, and continue until “Ga’al Ysrael”. Then take three steps forward in the manner of one approaching a king. (Chapter 18, Halacha 2)
Regarding the prohibition to cause an interruption between the blessing of redemption and the beginning of the Shemoneh Esrei, the question arises: Why aren’t these three steps considered an interruption? The Tehillah L’David (111:1) answers that. since it is necessary to take these three steps, they are not an interruption. This answer is certainly understandable according to the Ben Ish Chai, who explains that these steps are needed according to Kabbalah.