The famous mantra is
मङ्गलम् भगवान विष्णुः, मङ्गलम् गरुणध्वजः। मङ्गलम् पुण्डरी काक्षः, मङ्गलाय तनो हरिः॥
This is famous mantra Of Lord vishnu composed in weddings,so I want to know in which scripture/text this mantra is found?
In Garuda Puraana PretaKaanda (also called DharmaKaanda), chapter 47
लाभस्तेषां जयस्तेषां कुतस्तेषां पराजयः ।
येषामिन्दीवरश्यामो हृदयस्थो जनार्दनः ॥ ४५ ॥
धर्मो जयति नाधर्मः सत्यं जयति नानृतम् ।
क्षमा जयति न क्रोधो विष्णुर्जयति नासुराः ॥ ४६ ॥
विष्णुर्माता पिता विष्णुर्विष्णुः स्वजनबान्धवाः ।
येषामेव स्थिरा बुद्धिर्न तेषां दुर्गतिर्भवेत् ॥ ४७ ॥
मङ्गलं भगवान्विष्णुर्मङ्गलं गरुडध्वजः ।
मङ्गलं पुण्डरीकाक्षो मङ्गलायतनं हरिः ॥ ४८ ॥
हरिर्भागीरथी विप्रा विप्रा भागीरथी हरिः ।
भागीरथी हरिर्विप्राः सारमेतज्जगत्त्रये ॥ ४९ ॥
They get profits, they get victory, and where is their defeat, in whose heart is situated Janaardana Hari Who is black like the blue lotus. 45.
Always Dharma Righteousness wineth, never wineth Adharma Unrighteousness. Always Truth wineth and never wineth Falsehood. Always Forgiveness wineth, wineth not Anger. So doth always Vishnu(the God in our heart) win, and never win the Asuraas(the demons of bad qualities in us). 46.
Vishnu is Mother, Vishnu is Father, and Vishnu alone is the relatives and friends- in whom this knowledge is established, they never go to misfortune. 47.
He, Who is possessor of immense fortunes and Who pervadeth everything, is Auspiciousness.
He Whose emblem is Garuda, is Auspiciousness.
He Whose eyes are like lotus, is Auspiciousness.
He Who shineth exuberantly, is the Receptacle of all Auspiciousness. 48.
O Sages! Hari is the River Ganges, and O Sages! the River Ganges is Hari. Ganges is Hari, O Sages! Know this all as the essence in the three world. 49.