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SB 10.4.42

sa hi sarva-surādhyakṣo
 hy asura-dviḍ guhā-śayaḥ
tan-mūlā devatāḥ sarvāḥ
 seśvarāḥ sa-catur-mukhāḥ
ayaṁ vai tad-vadhopāyo
 yad ṛṣīṇāṁ vihiṁsanam
Synonyms: 
saḥ — He (Lord Viṣṇu); hi — indeed; sarva-sura-adhyakṣaḥ — the leader of all the demigods; hi — indeed; asura-dviṭ — the enemy of the asuras; guhā-śayaḥ — He is the Supersoul within the core of everyone’s heart; tat-mūlāḥ — taking shelter at His lotus feet; devatāḥ — the demigods exist; sarvāḥ — all of them; sa-īśvarāḥ — including Lord Śiva; sa-catuḥ-mukhāḥ — as well as Lord Brahmā, who has four faces; ayam — this is; vai — indeed; tat-vadha-upāyaḥ — the only means of killing Him (Viṣṇu); yat — which; ṛṣīṇām — of great sages, saintly persons, or Vaiṣṇavas; vihiṁsanam — suppression with all kinds of persecution.
Translation: 
Lord Viṣṇu, the Supersoul within the core of everyone’s heart, is the ultimate enemy of the asuras and is therefore known as asura-dviṭ. He is the leader of all the demigods because all the demigods, including Lord Śiva and Lord Brahmā, exist under His protection. The great saintly persons, sages and Vaiṣṇavas also depend upon Him. To persecute the Vaiṣṇavas, therefore, is the only way to kill Viṣṇu.
Purport: 

The demigods and the Vaiṣṇavas especially are part and parcel of the Supreme Lord, Viṣṇu, because they are always obedient to His orders (oṁ tad viṣṇoḥ paramaṁ padaṁ sadā paśyanti sūrayaḥ). The demoniac followers of Kaṁsa thought that if the Vaiṣṇavas, saintly persons and sages were persecuted, the original body of Viṣṇu would naturally be destroyed. Thus they decided to suppress Vaiṣṇavism. The asuras perpetually struggle to persecute the Vaiṣṇavas because they do not want Vaiṣṇavism to spread. Vaiṣṇavas preach only devotional service, not encouraging karmīs, jñānīs and yogīs, because if one must liberate oneself from material, conditional life, one must ultimately become a Vaiṣṇava. Our Kṛṣṇa consciousness movement is directed with this understanding, and therefore the asuras always try to suppress it.