In Igeret Hakodesh, Perek 30, the Alter Rebbe discusses the importance of Tzedakah, even during challenging times, emphasizing the need for regular giving. Referring to the Talmud's idea of "Kol pruta upruta," meaning every coin adds up, the Alter Rebbe also applies the Talmud's concept of G-d's awareness when one consistently attends shul but misses a day to the realm of Tzedakah.