सतां प्रसङ्गान्मम वीर्यसंविदो भवन्ति हृत्कर्णरसायना: कथा: । तज्जोषणादाश्वपवर्गवर्त्मनि श्रद्धा रतिर्भक्तिरनुक्रमिष्यति ॥
satāṁ prasaṅgān mama vīrya-saṁvido bhavanti hṛt-karṇa-rasāyanāḥ kathāḥ. taj-joṣaṇād āśv apavarga-vartmani śraddhā ratir bhaktir anukramiṣyati.- Bhagvatam 3.25.25
शुश्रूषो: श्रद्दधानस्य वासुदेवकथारुचि: । स्यान्महत्सेवया विप्रा: पुण्यतीर्थनिषेवणात् ॥
śuśrūṣoḥ śraddadhānasya vāsudeva-kathā-ruciḥ. syān mahat-sevayā viprāḥ puṇya-tīrtha-niṣevaṇāt.- Bhagvatam 1.2.16
These are a couple places in the Bhāgavatam where it's explained what the effect of doing saṅg (association) of a saint is. The saint, the true saint is sat (truth), and when we associate mentally with that saint, we are doing saṅg, so we do satsaṅg. And the effect of such satsaṅg is to develop a desire for God, and develop feelings of attachment and love for God, and start developing detachment from worldly pleasures.
All of this just happens from doing satsaṅg of a saint. So if you're doing the saṅg of a true saint, these internal transformations must start to take place. And this is how we judge.
If we are truly doing saṅg, if we are truly, sincerely associating with this saint, and following their instructions for how to do devotion, then we're bound to see this progress. This progress is the result of the purification of our heart, which is the result of receiving the grace of the saint. There's no other way to effect such powerful purification of the heart that you would actually see.
What? My worldly attachments reduced? I didn't do anything. All I did was satsaṅg of this saint. Now my attachments are reducing? It's unmistakable. What? I did so much bhakti in my life, but I never developed these feelings of love for God. How's it happening? It's through the grace of the saint.
So on one hand, recognizing a saint is very straightforward. Finding the true saint, that's another matter. It's best if we leave that up to Śhrī Kṛiṣhṇa. We just keep praying to Śhrī Kṛiṣhṇa, sincerely requesting Him to send a saint into our life, and leave that part up to Him. Keep praying sincerely until He does it.
But once He arranges that meeting, then it's very straightforward to recognize that you've received the saṅg of a true saint. Because you'll see these inner transformations take place. You yourself will experience it.
