金剛般若經依天親菩薩論贊略釋秦本義記卷上 1.112

1.112

[Sūtra:] "'Subhūti, I now speak to you truthfully: if a good man or good woman were to fill with the seven treasures as many three-thousandfold great-thousandfold world-systems as the sands in those Gaṅgā Rivers, and use them for giving, would that person obtain much merit?'"
This is the third [part], asking about the merit. "I now speak to you truthfully" means that, wishing to make the comparison, [the Buddha] first shows that the Tathāgata's speech is free of error. "If a good man [or good woman]", etc., additionally clarifies the capacity of the mind [of the donor]. "With the seven treasures" directly clarifies the measure of what is given. "Fill as many world-systems as the sands in those Gaṅgā Rivers" comprehensively shows the quantity of the given treasures.