One should say Tehillim for the honor of Hashem, may He be blessed, and not for any other motive.
Sources and Explanations
So wrote the Chida in the introduction to his book Yosef Tehillot (end of ot 8). It appears that his holy intent was that one should not have in mind that his reading is in order that all those wondrous segulot (spiritual remedies) stated regarding one who reads Tehillim should come upon him; rather, he should read them for the honor of the Creator, and those segulot will come on their own. This is just as we find in several other places. For example, in what is stated in the Gemara (Berachot 8b) that whoever completes his parashiyot (weekly Torah portions) with the tzibbur, twice Mikra (the Torah text) and once Targum (the Aramaic translation), his days and years are lengthened. And Sefer Chassidim (siman 301) wrote on this that one should read twice Mikra and once Targum for the sake of the One Who spoke and the world came into being: “and Hakadosh Baruch Hu (the Holy One, blessed be He) will automatically lengthen his days and years.”
Similarly, we find this with the mitzvah of mezuzah, regarding which it is stated: “And you shall write them upon the doorposts of your house and upon your gates, so that your days may be multiplied, and the days of your children” (Devarim 11:21). Chazal elaborated that the house is protected by the mezuzah (see Tur, Yoreh De’ah 285), and they likewise said in Perek HaKometz (33b) that the mezuzah should be placed in the tefach (handbreadth) closest to the public domain, so that the house will be protected from the outside. In contrast, the Rambam ruled (Hilchot Mezuzah 5:4) that one who performs this great mitzvah of mezuzah as if it were an amulet for his own benefit, for example, affixing it so that it will guard his house and he will have length of days through it, is “wasting the world.” To reconcile these statements, the Kesef Mishneh (ibid.) wrote that one should not have in mind, when performing the mitzvah, that it comes to protect the house; rather, he should intend to fulfill the commandment of the Creator, and the protection will follow automatically. And indeed, the Tur also concluded that nevertheless the intention of the one fulfilling it should be only to fulfill the commandment of the Creator, may He be exalted, Who commanded us regarding it. This is taken from his father, the Rosh (end of Hilchot Ketanot), who writes: “Rather, one should perform the mitzvah properly, to fulfill the commandment of the Creator, and He guards us and is our shade at our right hand.”
From the sefer “Shaf Veyativ – Laws of Saying Tehillim” by Rabbi Shay Tahan, Chapter 6: Intention (Kavanah) While Saying Tehillim, Halacha 3 (p. 87 in the print edition). Translated from the Hebrew original.
