Manusmriti
पाणिग्रहणसंस्कारः सवर्णासूपदिश्यते । असवर्णास्वयं ज्ञेयो विधिरुद्वाहकर्मणि ॥ ४३ ॥
The ceremony of joining the hands is prescribed for (marriages with) women of equal caste (varna); know that the following rule (applies) to weddings with females of a different caste (varna).
english translation
pANigrahaNasaMskAraH savarNAsUpadizyate । asavarNAsvayaM jJeyo vidhirudvAhakarmaNi ॥ 43 ॥
hk transliteration by Sanscript