Within अरण्यक पर्व of the वनपर्व of the महाभारत, there is an event when Yudhistira sets out to the forest as an outcome of losing the game of dice against the Kauravas. As he sets out, the citizens of Hastinapur approach him telling him that they too will accompany Yudhistira to the forest. This memorable exchange captures the benefit of सत्संग (association with good persons) where the citizens state that they perform to accompany a person who follows धर्म rather than stay back in the kingdom. Given the wisdom that is contained here can be beneficial to all, an extract of अरण्यक पर्व that articulates the benefit of सत्संग is captured below for everyone’s benefit. 

श्रूयतां चाभिदास्यामो गुणदोषान् नरर्षभाः। शुभाशुभाधिवासेन संसर्गः कुरुते यथा।।

O foremost of men! Listen to the गुण (सगुण)‌ & दोष, as we indicate, that respectively arise from associating with what is शुभ and what is अशुभ

वस्त्रमापस्तिलान् भूमिं गन्धो वासयते यथा। पुष्पाणाम् अधिवासेन तथा संसर्गजा गुणाः।।

Aa वस्त्र,‌ water, तिल and भूमि are perfumed by their association with पुष्पम्, so qualities are derived from association (with appropriate people)

मोहजालस्य योनिर्हि मूढैरेव समागमः। अहन्यहनिधर्मस्य योनिः साधुसमागमः॥

Association with मूढ‌ produces मोह (delusion or false infatuation) as daily association with a साधु (pure or honest) person produces धर्म.

तस्मात् प्राज्ञैश्च वृद्धैश्च सुस्वभावैस्तपस्विभिः। सद्भिश्च सह संसर्ग: कार्य: शमपरायणैः॥

Therefore, those who are virtuously inclined will associate with those who are wise, old, honest and pure in conduct and who are तपस्वी‌ (ascetics)

येषां त्रीण्यवदातानि विद्या योनिश्च कर्म च। ते सेव्यास्तैः समास्या हि शास्त्रेभ्योSपि गरीयसी॥

निरारम्भा ह्यपि वयं पुण्यशीलेषु साधुषु। पुण्यमेवाप्नुयामेह पापं पापोपसेवनात्।।

Those with triple possessions viz विद्या,‌ good birth (born in a good family) and कर्म (good actions) are pure and should be waited upon. To associate with them is superior to study of the शास्त्र. Without performing any special act of पुण्य,‌ we shall be able to reap the पुण्य by merely associating with साधु persons. We shall certainly get पापम् by associating and serving persons who perform पापकर्म (दुर्योधन in this case)

असतां दर्शनात् स्पर्शात् संजल्पाच्च सहासनात्। धर्माचाराः प्रहीयन्ते सिद्ध्यन्ति च न मानवाः।।

The very sight and touch of those who do पापकर्म and conversation ans association with them will cause diminution of one’s पुण्य (stock). Men (who act thus) never attain purity of आत्मा ( or आचरण of one who is a धार्मिक)

बुद्धिश्च हीयते पुंसां नीचैः सह समागमात्। मध्यमैर्मध्यतां याति श्रेष्ठतां याति चोत्तमैः॥

Association with the mean and low makes one’s understanding mean and low, association with the middling (or indifferent) makes one indifferent and associating with the best (उत्तम) makes one the best.

अनीचैर्नाप्यविषयैर्नाधर्मिष्ठैर्विशेषत:। ये गुणाः कीर्तिता लोकेधर्मकामार्थसम्भवाः। लोकाचारेषु सम्भूता वेदोक्ता: शिष्टसम्मताः।।

ते युष्मासु समस्ताश्च व्यस्ताश्चैवेह सद्गुणाः। इच्छामो गुणवन्मध्ये वस्तुं श्रेयोSभिकाङ्क्षिणः॥

All those attributes, which are spoken of in the world as the source of धर्म, अर्थ‌ & काम, which are highly regarded by humans, extolled in the वेद and approved by the good exist in you individually and collectively. Desiring our own welfare, we wish to live among men who possess such गुण.

Source:
Translation of Mahabharata by MN Dutt