The Rebbe's teaching that tzedakah brings blessing — for health, livelihood and every need — and what it does for the giver:
A vessel for blessing. Tzedakah is both a source of sustenance and a vessel to receive it (IK 493). G-d's promise of blessing for tzedakah is tangible; increasing one's giving each year brings more blessing (IK 3205). Wealth is entrusted to us as a test, and using it for tzedakah fulfills its purpose (IK 1884); make G-d a true partner in your business through tzedakah and honesty (IK 2033, 5833). Carefulness in tzedakah is directly connected to one's livelihood (IK 2496).
In financial difficulty. Increasing tzedakah is a powerful way to overcome obstacles in making a living (IK 3584, 7103), especially giving often and before prayer (IK 5686, 9118). Don't let worry take over — act, and give tzedakah (IK 8418). Even after a loss, don't despair; strengthen trust and give (IK 5805).
For health and family. Alongside the doctor's advice, tzedakah — together with Tehillim, Torah study and checked mezuzos — is among the Rebbe's most frequent recommendations for health and healing (IK 660, 801, 1398, 2704, 3902, 5053, 6132, 7127), and before surgery (IK 712). Tzedakah is also part of seeking blessing for children (IK 1604, 5157, 9130), and tzedakah by both husband and wife brings blessing to the whole family (IK 5073). Physically helping others, not only giving money, brings added blessing (IK 2705). Tzedakah is vital, but it doesn't replace daily Torah study and prayer (IK 1438).
What it does for the giver. Tzedakah uplifts the giver as much as the receiver (IK 7997); it refines character, brings redemption closer (IK 8595), and helps repair the past (IK 9008).
See also: Bitachon – Trusting G-d and doing your part; Health – Following the doctor's advice; Livelihood – Worry about money and trusting in G-d.