It is evident that all charity, kindness done without remembrance of God leads to further contamination of heart and, therefore, termed as sin. Sin is something, which should not be done, which has bad effects. You also do not know how the receiver will utilize your charity alms. Depending on the use of charity received, donor receives the effect. If the receiver puts charity to bad use, donor has to bear its effect. While donating, donor assumes that it will be put to good use and mind is not sure of end use of the donation and that is the reason why end use of charity matters.