As per Panini, it is साप्तपदीनं सख्यम्॥ - A relation accomplished through seven-steps, seven commitments for each other.Marriage is one form of friendship. In Atharva Veda, Atharva calls Varuna as his सप्त-पदी मित्र. आ ते स्तोत्राण्य् उद्यतानि यन्त्व् अन्तर् विश्वासु मानुषीषु दिक्षु | देहि नु मे यन् मे अदत्तो असि युज्यो मे सप्तपदः सखासि ||9|| समा नौ बन्धुर् वरुण समा जा वेदाहं तद् यन् नाव् एषा समा जा | ददामि तद् यत् ते अदत्तो अस्मि युज्यस् ते सप्तपदः सखास्मि ||10|| Mahabharata also concurs सप्त-पदी friendship. (Vana Parva 260.35, 297.23) सप्त-पदी needed to be observe under the witness of Fire, fire of individual, fire of local environment, fire of universe. In Ramayana, Raam and Sugriva friendship was considered Agni-Shakshi friendship) so.aham sabhaajyo bandhuunaam suhR^idaam caiva raaghava | yasya agni saakSikam mitram labdham raaghava va.mshajam || 4-8-4 "He who has gained the one born in Raghava-s dynasty as friend, to which sacred fire bore the witness, such a being like me is estimable among his relative, more so among his kind-hearted friends... [Kishkindha Kanda 4-8-4] ============================== What are seven commitments that you must have with all your best friends (सप्त-पदी friends including wife) ? 1. ॐ एकमिशे विष्णु: त्वा नयतु । First step for sap or food. 2. ॐ द्वे उर्जे विष्णु: त्वा नयतु । Second step for strength 3. ॐ त्रीणि राय्स्पोशाय विष्णु: त्वा नयतु । Third step for vows(vrata) 4. ॐ चत्वारि मायोभवाय विष्णु: त्वा नयतु । Fourth step for happiness 5. ॐ पञ्च पशुभ्यो विष्णु: त्वा नयतु । Fifth step for cattle (wealth) 6. ॐ षड रुतुभ्यों विष्णु: त्वा नयतु । Sixth step for all seasons 7. ॐ सखे सप्तपदा भव । Seventh step for Hotra(sacrificial rites) सखा सप्तपदा भव । सखायौ सप्तपदा बभूव । सख्यं ते गमेयम् । सख्यात् ते मायोषम् । सख्यान्मे मयोष्ठाः । At the end, be my friend for life. You have walked seven steps with me; be my friend. We have walked seven steps together; let us be friends. Let me get your friendship. Let me not part from your friendship. May you not part from my friendship.