Shiva Purana
गुरुश्च स्वाश्रितं शिष्यं वर्षमेकं परीक्षयेत् ॥ ५६ ब्राह्मणं क्षत्रियं वैश्यं द्विवर्षं च त्रिवर्षकम् ॥ ५६ ॥
The teacher shall test the brahmin disciple for a year, the kṣatriya for two years and the vaiśya for three years.
english translation
guruzca svAzritaM ziSyaM varSamekaM parIkSayet ॥ 56 brAhmaNaM kSatriyaM vaizyaM dvivarSaM ca trivarSakam ॥ 56 ॥
hk transliteration by Sanscript