There are three ways to give Tzedakah, corresponding to three approaches to serving Hashem. In the first way it’s about the giver-to train him to be giving. Here we tell the person to give up to 20%. The second level is when somebody approaches you for help. Now it’s about the receiver. Therefore, you must push yourself and give him even more than 20%. The third level, says the Alte Rebbe in Tanya, is that if someone is trying to correct/heal his soul, then he should be willing to give everything away. If you’re willing to give everything for the health of your body, then of course you should be willing to give everything away for the health of your soul. So too it is with serving Hashem. There is the basic level of trying to correct yourself, becoming a better person in a very systematic limited way. There’s a second level where you push yourself to go out of your comfort zone to help somebody else. Finally, there’s a third level where you completely change your life and devote yourself 100% to Hashem. לקו״ש כז