ויקחו לי תרומה (תרומה כה:ב)

The holy Baal Shem Tov zt’’l explained that it says the word “ויקחו” to take and not “ויתנו” to give because one who gives tzedakah is allowed to provide it even if it’s not לשם שמים (for the sake of a mitzvah).  Because at the end of the day, the poor person will derive satisfaction – the “לוקח”- the recipient has to accept the charity לשם שמים and use the money to feed himself and his family, and not to use the money for extras.