Apostle Paul dealt extensively with the subject of giving in his epistle to the Corinthians. Specifically, two chapters in his second epistle to them are exclusively on this subject. In chapter 8:7, he praised them for their gift of faith, utterance, and knowledge as well as their diligence.
In chapter 9, he showed them how to give acceptably and the manifold blessings of giving. In our text, two blessings are identified. Firstly, the recipient of our generosity is blessed. What you give to others, particularly those who are less privileged, helps to supply their needs. Secondly, God is blessed through your giving. Someone may be wondering how can God be blessed by man. God is blessed because those who benefit from your kindness praise Him. Praising God means blessing Him.
The giver is the third person who is blessed by the exercise. How does this happen? Those who receive your substance will not only bless God in praise and thanksgiving, but they will also lift up their voice of intercession on your behalf. They ask God to bless you in return and preserve all that is yours. So giving creates a cycle of blessing where God, the giver, and the recipient are blessed. With the manifold blessings attached to giving, it is not surprising that the devil is vehemently opposed to its practice.