The devotees of the Lord do not bother about the impersonal Brahman conception of God; their faith and devotion bring them to surrender immediately unto the Supreme Lord, and out of the causeless mercy of Kṛṣṇa they can understand Kṛṣṇa. No one else can understand Him. So even great sages agree: What is ātmā, what is the Supreme? It is He whom we have to worship.
(Bhagavad-Gita-------10:2--------purport).

According to the law of karma, everyone is destined to suffer or enjoy according to a certain material standard, but the mercy of Lord Kṛṣṇa is so powerful that the Lord can change all the reactions of one's past karma, or fruitive activities. Lord Śrī Caitanya Mahāprabhu specifically drew attention to the mercy of Lord Kṛṣṇa. That mercy is more powerful than anything else, for it had saved Raghunātha dāsa from the strong bondage of materialistic life, which the Lord compared to a hole where people pass stool. Śrī Caitanya Mahāprabhu gave His verdict that those addicted to the materialistic way of life are like worms that are living in stool but cannot give it up.
(Sri Caitanya Caritamrta-------3:6:193-------purport).

Sometimes, however, it is found that without undergoing any devotional process, one all of a sudden develops devotion for Lord Kṛṣṇa. This sudden development of the devotional attitude in a person must be understood as a special mercy of Kṛṣṇa or of His devotee. This apparently accidental development of ecstatic feelings through the causelessmercy of Kṛṣṇa can be divided into three groups: simply by speaking, simply by glancing and simply by good wishes.
(Nectar of Devotion).

If one who is performing the Vedic ritualistic ceremonies becomes a devotee, even if he is a gṛhastha, he can receive the causeless mercy of Kṛṣṇa. The objective of a devotee is to return home, back to Godhead. Such a devotee, even though not performing ritualistic ceremonies, advances in spiritual consciousness by the supreme will of the Personality of Godhead. One may actually become successful in spiritual consciousness by the mercy of devotees, or one may fall from spiritual consciousness by being disrespectful to devotees.
(Srimad Bhagavatam-----7:15-------summary).

Kṛṣṇa can become the director and spiritual master of anyone who is serious about getting the mercy of Kṛṣṇa. The Lord sends the spiritual master to train a devotee, and when the devotee is advanced, the Lord acts as the spiritual master within his heart.
(Bhagavad-Gita-------7:15:76--------purport).

As soon as the Kṛṣṇa sun is arisen within one's heart, the darkness of materialistic speculations about the Absolute Truth and the living beings is at once cleared off. In the presence of the sun, the darkness cannot stand, and the relative truths that were hidden within the dense darkness of ignorance become clearly manifested by the mercy of Kṛṣṇa, who is residing in everyone's heart as the Supersoul.
(Srimad Bhagavatam-----1:2:21-------purport).

There is a path toward liberation in the higher planetary systems and a path toward the hellish planets, but a nārāyaṇa-para devotee is unafraid wherever he is sent; he simply wants to remember Kṛṣṇa, wherever he may be. Such a devotee is unconcerned with hell and heaven; he is simply attached to rendering service to Kṛṣṇa. When a devotee is put into hellish conditions, he accepts them as Kṛṣṇa's mercy: tat te 'nukampāṁ susamīkṣamāṇaḥ (S.B.10:14:8). He does not protest, "Oh, I am such a great devotee of Kṛṣṇa. Why have I been put into this misery?" Instead he thinks, "This is Kṛṣṇa's mercy." Such an attitude is possible for a devotee who engages in the service of Kṛṣṇa's representative. This is the secret of success.
(Srimad Bhagavatam-----6:1:16-------purport).

Thus the transcendental causeless mercy of Lord Kṛṣṇa is manifested in the heart of the devotee. At such a time, material needs no longer exist. The lamentation that invariably accompanies material desires also vanishes. By the grace of the Lord one is elevated to the transcendental position, and then the transcendental mellows of the spiritual world are manifested in him. One's devotional service then becomes firm, and one engages in the Lord's transcendental loving service with great determination. All these combine to fully awaken the devotee's heart with love of Kṛṣṇa.
(Sri Caitanya Caritamrta-------2:10:119-------purport).

When a devotee is never tired of executing devotional service and is always engaged in Kṛṣṇa conscious activities, constantly relishing the transcendental mellows in relationship with Kṛṣṇa, he is called perfect. This perfectional stage can be achieved in two ways: one may achieve this stage of perfection by gradual progress in devotional service, or one may become perfect by the causeless mercy of Kṛṣṇa, even though he has not executed all the details of devotional service.
(Nectar of Devotion).

The sinful and the destitute can understand their mistakes and misfortune only by Lord Kṛṣṇa's mercy. Once they begin to repent for their sins and surrender to the Lord, they are saved; they become purified and start manifesting saintly characteristics. And if even after a person takes to the devotional process some vestige of immorality remains in his character, that also will soon be eradicated by the Lord's grace. The single-minded devotee who never offends the Supreme Lord or His devotees is to be considered a saintly soul. Even if it seems that such a saint is not yet rid of all sinful propensities, he will never be destroyed, as are the yogīs and karmīs in a similar situation. This the Supreme Lord Himself has declared.
(Renunciation through Wisdom).

Kṛṣṇa and His name, fame, qualities and paraphernalia cannot be materially understood. Unless one is advanced in spiritual life (sevonmukhe hi jihvādau), one cannot see Kṛṣṇa. Therefore the ability to see Kṛṣṇa depends on Kṛṣṇa's mercy. The same privilege of being seen or unseen according to one's own desire was given to Mahārāja Nimi. Thus he lived in his original, spiritual body as an associate of the Supreme Personality of Godhead.
(Srimad Bhagavatam-----9:13:11-------purport).