In Kali-yuga, Lord Caitanya mercifully gives love of Krishna through chanting alone, requiring no qualification.Listen — Srila Prabhupada Uvaca
Prabhupāda: satya-yuge dharma-dhyāna karāya 'śukla'-mūrti dhari' kardamake vara dilā yeìho kṛpā kari' [Cc Madhya 20.334] [As the white incarnation, the Lord taught religion and meditation. He offered benedictions to Kardama Muni, and in this way He showed His causeless mercy.] In the Satya-yuga the incarnation of God is of white color. kṛṣṇa-'dhyāna' kare loka jñāna-adhikārī tretāra dharma 'yajña' karāya 'rakta'-varṇa dhari' [Cc Madhya 20.335] [In Satya-yuga the people were generally advanced in spiritual knowledge and could meditate upon Kṛṣṇa very easily. The people’s occupational duty in Tretā-yuga was to perform great sacrifices. This was induced by the Personality of Godhead in His reddish incarnation.] So in the Satya-yuga, the age of goodness, in that age the meditation was possible.
Kṛte yad dhyāyato viṣṇuṃ tretāyāṃ yajato makhaiḥ [SB 12.3.52]. [Whatever result was obtained in Satya-yuga by meditating on Viṣṇu, in Tretā-yuga by performing sacrifices, and in Dvāpara-yuga by serving the Lord's lotus feet can be obtained in Kali-yuga simply by chanting the Hare Kṛṣṇa mahā-mantra.] According to injunction of Śrīmad-Bhāgavatam, meditation is possible in the age of goodness, when cent percent people were all in the modes of goodness. There are three modes of nature: modes of goodness, modes of passion and modes of ignorance. Similarly, the ages are also conducted by the three modes of material nature. Just like there are seasonal changes—in our experience in one year sometimes it is summer, sometimes it is winter, sometimes it is spring—similarly, in course of nature's way there are different yugas, millennium. So in the Satya-yuga people are all in the modes of goodness.
Therefore, at that time they could concentrate the mind in the Supreme, and meditation was recommended at that time. Kṛṣṇa-'dhyāna' kare loka jñāna-adhikārī. Jñāna-adhikārī means they were quite fit to understand spiritual knowledge. Because without developing the modes of goodness, nobody can understand spiritual knowledge.
In the ignorance, the lowest grade of men, they are in ignorance. The ignorance, the symptom of ignorance we have already described in the Śrīmad Bhagavad-gītā. Ignorance means laziness. Laziness. That is ignorance.
And passion means active. And goodness means sober. So we cannot find all men in this world of the same quality. Some of them are in goodness; some of them are in passion; some of them are in ignorance.
But in this age, seventy-five percent or more than that, they are in ignorance. And maybe ten or fifteen percent in passion, and hardly five percent, they are in goodness. Therefore majority population of this age, they cannot perform meditation or great sacrifices or temple worship. They cannot. Therefore Lord Caitanya has, by His causeless mercy...
Of course, it is according to the Vedic injunction. Kṛte yad dhyāyato viṣṇum [SB 12.3.52]. [Whatever result was obtained in Satya-yuga by meditating on Viṣṇu, in Tretā-yuga by performing sacrifices, and in Dvāpara-yuga by serving the Lord's lotus feet can be obtained in Kali-yuga simply by chanting the Hare Kṛṣṇa mahā-mantra.] The same achievement which was obtained in the age of goodness by meditation was achieved in the next age by sacrifices and the next age by temple worship. At the present age it is recommended to achieve that success, that perfection, spiritual perfection, by hari-kīrtanāt, by chanting Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare / Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. It doesn't require any previous qualification to chant Hare Kṛṣṇa. Anybody and everybody can join, and by chanting this, the result will be that progressive chanting will help him in cleansing the dust on the mirror of the mind. The whole trouble in the world is misunderstanding.