Manusmriti
द्विकं त्रिकं चतुष्कं च पञ्चकं च शतं समम् । मासस्य वृद्धिं गृह्णीयाद् वर्णानामनुपूर्वशः ॥ १४२ ॥
Just two in the hundred, three, four, and five (and not more), he may take as monthly interest according to the order of the castes (varna).
english translation
dvikaM trikaM catuSkaM ca paJcakaM ca zataM samam । mAsasya vRddhiM gRhNIyAd varNAnAmanupUrvazaH ॥ 142 ॥
hk transliteration by Sanscript