A tradition from the Baal Shem Tov in the name of his teacher* is that from the second day of Rosh Chodesh Elul [alef Elul] through Yom Kippur, three kapitlach Tehillim should be recited daily, i.e., 1, 2, 3 on alef Elul, 3, 4, 5 on beis Elul, and so on. The last thirty-six kapitlach should be recited on Yom Kippur itself, nine before Kol Nidrei, nine before Krias Shma She’al Hamitah, nine after Mussaf, and nine after Neilah.
==== Based on Kovetz Michtovim, caption: From the reshimos of the Rebbe RaYYatz
*Achiya haShiloni was sent to teach the Baal Shem Tov Torah for ten years, from when the Baal Shem Tov was age 26 until age 36. Sefer Hatoldos Rebbe Yisroel Baal Shem Tov by Harav Avrohom Ch. Glitzenshtein, pg. 35, caption “Shliach Min Hashomayim"
U FARATZTA
RABBI SHALOM BER MUNITZ