In Berakhot 14a (Daf Yomi a few days back), the Sages use metaphor — “as if” [כְּאִלּוּ, k’ilu] — to highlight the impact of certain behaviors:
אָמַר רַב: כָּל הַנּוֹתֵן שָׁלוֹם לַחֲבֵירוֹ קוֹדֶם שֶׁיִּתְפַּלֵּל כְּאִילּוּ עֲשָׂאוֹ בָּמָה
Rav said: Anyone who greets another person in the morning before he prayed, it is as if he built an altar [or “high place”].
כָּל הָעוֹשֶׂה חֲפָצָיו קוֹדֶם שֶׁיִּתְפַּלֵּל — כְּאִלּוּ בָּנָה בָּמָה
Rabbi Yona said that Rabbi Zeira said: Anyone who tends to his own affairs before he prays, it is as though he built an altar.
— B. Ber 14a
There is a “Jastrow Jackpot” (verse translation within a dictionary entry) for 14a under the word “shalom,” as in “giving peace” or “greeting”:
Ber. 14ᵃ משיב ש׳ וכ׳ may return a salutation to any person. Ib. כל הנותן ש׳ וכ׳ he who offers salutation to his neighbor before prayer, is considered as if he made him a highplace (worshipping man before God).
There is following and prior discussion about whether greeting someone before or during prayer is a matter of respect. Conclusions drawn, about when to greet without disrespecting either God or other people, are matter for another time. Here I just want to add “as if he built an altar” to the list of methods for for decision-making.
In his My Jewish Learning essay on Berakhot 15, Rabbi Asher Lopatin of Yeshivat Chovevei Torah Rabbinical School, discusses a more positive use of the concept of “altar,” that is, “the idea of elevating the human being to the level of an altar.”
In Berakhot 15, and many other places in the Talmud, the Sages portray ordinary activities of body or home as positive substitutes for Temple worship, which is no longer available. But here, in Berakhot 14, “altar” stands in for building an altar apart from the Temple (perhaps while it still stood) for the purposes of idol worship.
Together, both positive and negative metaphors around “altar” are part of re-drawing mundane word, thought, and action “as if” of cosmic importance.
In the interest of being thorough, here is how Jastrow explains the expression that introduces the metaphor:
אִילּוּ , אִלּוּ [ilu] is a contraction of אִם [im, if] and לוּ [lu, “would that” or “oh that”], maybe something like, “if it were that” — or, more simply: “if.” So, “כְּאִלּוּ” [k’ilu] is “as if.”