Mad-deva-saṅgāt means one who has absolutely taken the shelter of Kṛṣṇa's lotus feet, mad-deva. There are many others. Of course nobody is deva; deva is Kṛṣṇa. But there are others, demigods. There are thirty-three millions of devas. But Kṛṣṇa especially says mad-deva, one who has taken Kṛṣṇa as the only worshipable Deity. Sarva-dharmān parityajya mām ekam (BG 18.66), that is. One who has taken such vow, that kṛṣṇas tu bhagavān svayam (SB 1.3.28), "I shall take to the shelter of Kṛṣṇa," that is not very easy thing. But that is the ultimate point.
Bahūnāṁ janmanām ante jñānavān māṁ prapadyate (BG 7.19). That mad-deva, that "Kṛṣṇa, is my worshipable Deity only," this conclusion comes after many, many births of culturing knowledge, jñāna, yoga, karma. It is not so easy. Therefore we have to take shelter of such person who has taken Kṛṣṇa as the only shelter, vāsudevaḥ sarvam iti sa mahātmā (BG 7.19). We have to take shelter of such mahātmā, not others. Mad-deva, these are the different items, mad-deva-saṅgād guṇa-kīrtanān me. Not that now they have invented that "Why Hare Kṛṣṇa? We can chant śivo 'ham, śivo 'ham, om, om, kālī, kālī, durgā." They are all nonsense. They are all nonsense. Here bhakti-yoga means, here it is: guṇa-kīrtanān me. Not others. You cannot argue that "This is also good, that is also good." No compromise, kṛṣṇa-kīrtana. Just like Gosvāmīs, they said, kṛṣṇotkīrtana-gāna-nartana-parau. Not others. Utkīrtana, Hare Kṛṣṇa. Kīrtanād eva kṛṣṇasya mukta-saṅgaḥ paraṁ vrajet (SB 12.3.51). These are the instructions. Śravaṇaṁ kīrtanaṁ viṣṇoḥ (SB 7.5.23), not of Śiva, not of Brahmā, not of any other demigod. Śravaṇaṁ kīrtanaṁ viṣṇoḥ smaraṇaṁ pāda-sevanam. Here also it says, guṇa-kīrtanān me.