Shiva Purana
पापिनां च यथा संगात्तत्पापात्पतितो भवेत् ॥ यथेह वह्निसंपर्कान्मलं त्यजति कांचनम् ॥ २६ ॥
Associating with sinners will lead to sinful reactions. Just as gold in this world gives up its impurities when it comes into contact with fire.
english translation
pApinAM ca yathA saMgAttatpApAtpatito bhavet ॥ yatheha vahnisaMparkAnmalaM tyajati kAMcanam ॥ 26 ॥
hk transliteration by Sanscript