SB 3.29.8

abhisandhāya yo hiṁsāṁ
 dambhaṁ mātsaryam eva vā
saṁrambhī bhinna-dṛg bhāvaṁ
 mayi kuryāt sa tāmasaḥ
Synonyms: 
abhisandhāya — having in view; yaḥ — he who; hiṁsām — violence; dambham — pride; mātsaryam — envy; eva — indeed; — or; saṁrambhī — angry; bhinna — separate; dṛk — whose vision; bhāvam — devotional service; mayi — to Me; kuryāt — may do; saḥ — he; tāmasaḥ — in the mode of ignorance.
Translation: 
Devotional service executed by a person who is envious, proud, violent and angry, and who is a separatist, is considered to be in the mode of darkness.
Purport: 

It has already been stated in the Śrīmad-Bhāgavatam, First Canto, Second Chapter, that the highest, most glorious religion is the attainment of causeless, unmotivated devotional service. In pure devotional service, the only motive should be to please the Supreme Personality of Godhead. That is not actually a motive; that is the pure condition of the living entity. In the conditioned stage, when one engages in devotional service he should follow the instruction of the bona fide spiritual master in full surrender. The spiritual master is the manifested representation of the Supreme Lord because he receives and presents the instructions of the Lord, as they are, by disciplic succession. It is described in Bhagavad-gītā that the teachings therein should be received by disciplic succession, otherwise there is adulteration. To act under the direction of a bona fide spiritual master with a motive to satisfy the Supreme Personality of Godhead is pure devotional service. But if one has a motive for personal sense gratification, his devotional service is manifested differently. Such a man may be violent, proud, envious and angry, and his interests are separate from the Lord’s.

One who approaches the Supreme Lord to render devotional service but who is proud of his personality, envious of others or vengeful is in the mode of anger. He thinks that he is the best devotee. Devotional service executed in this way is not pure; it is mixed and is of the lowest grade, tāmasaḥ. Śrīla Viśvanātha Cakravartī Ṭhākura advises that a Vaiṣṇava who is not of good character should be avoided. A Vaiṣṇava is one who has taken the Supreme Personality of Godhead as the ultimate goal of life, but if one is not pure and still has motives, then he is not a Vaiṣṇava of the first order of good character. One may offer his respects to such a Vaiṣṇava because he has accepted the Supreme Lord as the ultimate goal of life, but one should not keep company with a Vaiṣṇava who is in the mode of ignorance.