SB 10.12.39
sakrd yad-anga-pratimantar-ahita
manomayi bhagavatim dadau gatim
sa eva nityatma-sukhanubhuty-abhi-
vyudasta-mayo ’ntar-gato hi kim punah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
If even only once or even by force one brings the form of the Supreme Personality of Godhead into one’s mind, one can attain the supreme salvation by the mercy of Krsna, as did Aghasura. What then is to be said of those whose hearts the Supreme Personality of Godhead enters when He appears as an incarnation, or those who always think of the lotus feet of the Lord, who is the source of transcendental bliss for all living entities and by whom all illusion is completely removed?
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The process for receiving the favor of the Supreme Personality of Godhead is described here. Yat-pada-pankaja-palasa-vilasa-bhaktya (Bhag. 4.22.39). Simply by thinking of Krsna, one can attain Him very easily. Krsna is also described as having His lotus feet always within the hearts of His devotees (bhagavan bhakta-hrdi sthitah). In the case of Aghasura, one may argue that he was not a devotee. The answer to this is that he thought of Krsna for a moment with devotion. Bhaktyaham ekaya grahyah. Without devotion, one cannot think of Krsna; and, conversely, whenever one thinks of Krsna, one undoubtedly has devotion. Although Aghasura’s purpose was to kill Krsna, for a moment Aghasura thought of Krsna with devotion, and Krsna and His associates wanted to sport within Aghasura’s mouth. Similarly, Putana wanted to kill Krsna by poisoning Him, but Krsna took her as His mother because He had accepted the milk of her breast. Svalpam apy asya dharmasya trayate mahato bhayat (Bg. 2.40). Especially when Krsna appears as an avatara, anyone who thinks of Krsna in His different incarnations (ramadi-murtisu kala-niyamena tisthan), and especially in His original form as Krsna, attains salvation. There are many instances of this, and among them is Aghasura, who attained the salvation of sarupya-mukti. Therefore the process is satatam kirtayanto mam yatantas ca drdha-vratah (Bg. 9.14). Those who are devotees always engage in glorifying Krsna. Advaitam acyutam anadim ananta-rupam: when we speak of Krsna, we refer to all His avataras, such as Krsna, Govinda, Narayana, Visnu, Lord Caitanya, Krsna-Balarama and Syamasundara. One who always thinks of Krsna must attain vimukti, special salvation as the Lord’s personal associate, not necessarily in Vrndavana, but at least in Vaikuntha. This is called sarupya-mukti.