The Hebrew comes through a doubling of the verb: pato’ach tif’tach, literally “(to) open you shall open”.
The doubling of a verb for the sake of emphasis is common.
Another example is the second paragraph of the Shema, which instructs us, shamo’a tishm’u – “you shall surely listen (to God’s commandments)” (Deut. 11:13). Translators sometimes render the extra verb with the English adverb “diligently” – e.g. “you shall listen diligently”.
In the case of charity the rabbinic commentators explained that there were two possibilities. A person had to respond when a poor man asked for charity (pato’ach) – but also when the poor man needed help but did not ask for it, perhaps because of embarrassment (tif’tach).
Charity is valuable whether it is reactive or pro-active, whether one gives when asked or without an actual request.
A good citizen does not wait. He sees what is happening around him and offers a supportive hand on his own initiative.