He said this, not because he was concerned about the poor, but because he was a thief, and as (echōn | ἔχων | pres act ptcp nom sg masc) keeper (echōn | ἔχων | pres act ptcp nom sg masc) of (echōn | ἔχων | pres act ptcp nom sg masc) the money box, he used to help himself to what was put into it.
Reference
John 12:6
Sequence
239