If a yogi wants to shatter the mountain of dirt (in the form of desires to lord it over material nature) in his mind, he should concentrate on the lotus feet of the Lord and not imagine something void or impersonal
SB Canto 3
The blessed Lord Śiva becomes all the more blessed by bearing on his head the holy waters of the Ganges, which has its source in the water that washed the Lord's lotus feet. The Lord's feet act like thunderbolts hurled to shatter the mountain of sin stored in the mind of the meditating devotee. One should therefore meditate on the lotus feet of the Lord for a long time.
In this verse the position of Lord Śiva is specifically mentioned. The impersonalist suggests that the Absolute Truth has no form and that one can therefore equally imagine the form of Viṣṇu or Lord Śiva or the goddess Durgā or their son Gaṇeśa. But actually the Supreme Personality of Godhead is the supreme master of everyone. In the Caitanya-caritāmṛta (CC Adi 5.142) it is said, ekale īśvara kṛṣṇa, ara saba bhṛtya: the Supreme Lord is Kṛṣṇa, and everyone else, including Lord Śiva and Lord Brahmā—not to mention other demigods—is a servant of Kṛṣṇa. The same principle is described here. Lord Śiva is important because he is holding on his head the holy Ganges water, which has its origin in the foot-wash of Lord Viṣṇu. In the Hari-bhakti-vilāsa, by Sanātana Gosvāmī, it is said that anyone who puts the Supreme Lord and the demigods, including Lord Śiva and Lord Brahmā, on the same level, at once becomes a pāṣaṇḍī, or atheist. We should never consider that the Supreme Lord Viṣṇu and the demigods are on an equal footing.
Another significant point of this verse is that the mind of the conditioned soul, on account of its association with the material energy from time immemorial, contains heaps of dirt in the form of desires to lord it over material nature. This dirt is like a mountain, but a mountain can be shattered when hit by a thunderbolt. Meditating on the lotus feet of the Lord acts like a thunderbolt on the mountain of dirt in the mind of the yogī. If a yogī wants to shatter the mountain of dirt in his mind, he should concentrate on the lotus feet of the Lord and not imagine something void or impersonal. Because the dirt has accumulated like a solid mountain, one must meditate on the lotus feet of the Lord for quite a long time. For one who is accustomed to thinking of the lotus feet of the Lord constantly, however, it is a different matter. The devotees are so fixed on the lotus feet of the Lord that they do not think of anything else. Those who practice the yoga system must meditate on the lotus feet of the Lord for a long time after following the regulative principles and thereby controlling the senses.
It is specifically mentioned here, bhagavataś caraṇāravindam: one has to think of the lotus feet of the Lord. The Māyāvādīs imagine that one can think of the lotus feet of Lord Śiva or Lord Brahmā or the goddess Durgā to achieve liberation, but this is not so. Bhagavataḥ is specifically mentioned. Bhagavataḥ means "of the Supreme Personality of Godhead, Viṣṇu," and no one else. Another significant phrase in this verse is śivaḥ śivo 'bhūt. By his constitutional position, Lord Śiva is always great and auspicious, but since he has accepted on his head the Ganges water, which emanated from the lotus feet of the Lord, he has become even more auspicious and important. The stress is on the lotus feet of the Lord. A relationship with the lotus feet of the Lord can even enhance the importance of Lord Śiva, what to speak of other, ordinary living entities.