אנטיגנוס איש סוכו קיבל משמעון הצדיק. הוא היה אומר, אל תהיו כעבדים המשמשין את הרב, על מנת לקבל פרס, אלא הוו כעבדים המשמשין את הרב, על מנת שלא לקבל פרס; ויהי מורא שמיים עליכם.
That does not mean that there is no reward; rather, there certainly is sechar veOnesh -- and that is part of why reality is just -- but that should not be your reason for performing mitzvot.
So why take a mitzvah that people are going to be doing anyway, and transform it into a segulah?! From Zechus Avos, about Chanukkah segulos:
The Gemara (Shabbos 23b) says that one who habitually lights candles will have sons that are Talmidei Chachomim. Rashi explains that the posuk (Mishlei 6, 23) says כִּי נֵר מִצְוָה וְתוֹרָה אוֹר - "the candle is a mitzvah and the Torah is light". By lighting candles of mitzvah, Shabbos candles and the Chanuka Menorah, one will merit what the Gemara says.And we have the Rif giving the same explanation. Bli neder, my own (divergent) explanation in a subsequent post.
But what frum Jewish woman does not light neros Shabbos? (Though see Tosafot, about two lights and two talmidei Chachamim.) And what frum Jewish man does not light neros Chanukkah for his household? And yet, even after this ritualization of neros Shabbos, not everyone is a talmid chacham, even from frum families. Why?
But forget about the why not every family has talmidei Chachamim. Let us focus elsewhere.
Specifically, everyone is going to do it anyway. Why give this as a Chanukkah segulah? Is there going to be anyone who will say, "well, I wasn't planning on fulfilling this mitzvah, but now that it is a segulah, I will certainly perform it?" I would hope not -- that would be very depressing.
To label a mitzvah a "segulah" cheapens it, IMHO. The mitzvos are not witchcraft, where the focus is to acheive (magically) some aim. They are fulfillments of Hashem's command, or else the Rabbis' command, to acheive specific aims -- to publicize the nes Chanukkah and perhaps internalize and spread the message behind Chanukkah. And the lighting of Shabbos candles is for the purpose of Shalom Bayis.
IMHO, if person A lights Chanukkah candles to fulfill the mitzvah, and person B lights candles as a segulah for having specific types of sons, I would say that person A has fulfilled the mitzvah better, and perhaps is even more likely to see the promised reward than person B. Because the pasuk says "Ki Ner Mitzvah veTorah Or." It does not say "Ki Ner Kishuf veTorah Or."
Another segulah, associated with lighting candles, is to turn a specific kepittel of Tehillim into an incantation, by making ritual repetition in a specific context a method of guaranteeing some practical aim. Perhaps as Bilaam used repetitions of 7 to try ensure some result, and as we see in all sorts of ANE and modern incancations.
The Baal Shem Tov to say וִיהִי נֹעַם and יֹשֵׁב בְּסֵתֶר עֶלְיוֹן, (last posuk of Tehilim 90, and the whole Chapter 91, with the last posuk of chapter 91 repeated twice) 7 times after lighting the Menorah. This is a segula to protect from many calamities. (Ramban says to say each word 7 times, but I haven't seen anyone do it like that. I've only seen people saying the whole chapter 7 times.)When the Baal Shem Tov said it, or when the Ramban said it -- I would not label that a magical incantation. (Though I would like to see that Ramban inside, to try to understand it -- where is it?? repeating each word individually 7 times has the general effect of taking it out of its context, making it more of a magic word rather than saying a pasuk in praise or prayer to Hashem.) They were operating within a specific mystical system, and so they attributed specific meanings to this. But to promulgate this to followers of segulahs (who seek out segulas for all occassions), among lists of many other segulahs to be ritually performed as kosher magic -- I find that more problematic.
The eating of a festive meal also gets transformed into a segulah, for healing:
In Shulchan Aruch (570, 2) it says that eating a meal for Chanuka is a סעודת הרשות, a non-obligatory meal. Chazal (Berachos 60a) say that Hashem gave רשות (permission) for doctors to heal. This is what סעודת הרשות alludes to; eating a special meal in honor of Chanuka, which is a special time for healing, can bring about healing. (Shaar Yisaschor, Yimei Orah 72)It is extremely unlikely that this is what the Shulchan Aruch meant. This is just free association. Much more likely, it means something along the lines of this.