Shrimad Bhagavatam 1.2.16 says: susrusoh sraddadhanasya
vasudeva-katha-rucih
syan mahat-sevaya viprah
punya-tirtha-nisevanat
Translation:
"O twice-born sages, by serving those devotees who are completely freed from all vice, great service is done. By such service, one gains affinity for hearing the messages of Vasudeva."
Purport by His Divine Grace Srila A.C. Bhaktivedanta Swami Prabhupada:
"The conditioned life of a living being is caused by his revolting against the Lord. There are men called devas, or godly living beings, and there are men called asuras, or demons, who are against the authority of the Supreme Lord. In the Bhagavad-gita (Sixteenth Chapter) a vivid description of the asuras is given, in which it is said that the asuras are put into lower and lower states of ignorance life after life and so sink to the lower animal forms and have no information of the Absolute Truth, the Personality of Godhead. These asuras are gradually rectified to God consciousness by the mercy of the Lord's liberated servitors in different countries according to the supreme will. Such devotees of God are very confidential associates of the Lord, and when they come to save human society from the dangers of godlessness, they are known as empowered incarnations of the Lord, as sons of the Lord, as servants of the Lord or as associates of the Lord. But none of them falsely claims that he is himself God. This is a blasphemy declared by the asuras, and the demoniac followers of such asuras also accept pretenders as God or His incarnation. In the revealed scriptures there is definite information of the incarnation of God. No one should be accepted as God or an incarnation of God unless he is confirmed by the revealed scriptures.
The servants of God are to be respected as God by the devotees who actually want to go back to Godhead. Such servants of God are called mahatmas, or tirthas, and they preach according to particular time and place. The servants of God urge people to become devotees of the Lord. They never tolerate being called God. Sri Chaitanya Mahaprabhu was God Himself according to the indication of the revealed scriptures, but He played the part of a devotee. People who knew Him to be God addressed Him as God, but He used to block His ears with His hands and chant the name of Lord Visnu. He strongly protested against being called God, although undoubtedly He was God Himself. The Lord behaves so to warn us against unscrupulous men who take pleasure in being addressed as God.
The servants of God come to propagate God consciousness, and intelligent people should cooperate with them in every respect. By serving the servant of God, one can please God more than by directly serving the Lord. The Lord is more pleased when He sees that His servants are properly respected because such servants risk everything for the service of the Lord and so are very dear to the Lord. The Lord declares in the Bhagavad-gita (18.69) that no one is dearer to Him than one who risks everything to preach His glory. By serving the servants of the Lord, one gradually gets the quality of such servants, and thus one becomes qualified to hear the glories of God. The eagerness to hear about God is the first qualification of a devotee eligible for entering the kingdom of God." (SB 1.2.16)
The best way for one to become qualified to enter into the Kingdom of God, from which having gone, one never returns to this temporary world full of miseries, is an eagerness to simply hear about the glories of the Lord. The recommended process for acquiring this eagerness is by serving the Lord's pure devotee.
Shrila Prabhupada explains here how the servant of the Lord comes to this world to spread God Consciousness. And they may appear in different countries according to the Lord's will. They are so magnanimous, they appear in different times and circumstances to reach the fallen conditioned souls wandering in this world. Similarly, the Lord incarnates in every species of life, in every universe. "There are innumerable material universes, and in each and every universe there are innumerable planets inhabited by different grades of living entities in different modes of nature. The Lord (Vishnu) incarnates Himself in each and every one of them and in each and every type of living society. He manifests His transcendental pastimes amongst them just to create the desire to go back to Godhead. The Lord does not change His original transcendental position, but He appears to be differently manifested according to the particular time, circumstances and society." (SB 1.2.34, Purport)
The pure devotee and the Lord are to be considered as One. Although they always maintain their independent identity, because they are flawlessly merged within the will of Krishna, they are to be respected as on the same level as God. Such goes for all servants of Krishna who are directly and fully engaged in Krishna consciousness through devotional service under the guidance of the bonafide spiritual master. It is stated in the sastra that even if one chants the holy name once without offense, they are rid of lifetimes of sinful results. So what to speak of the servants of Krishna who are constantly uttering the holy name and serving the pure devotee faithfully and with determination. We should always offer our respects to the servants of Lord Krishna, at least internally, understanding them to be the dispensers of the Lord's mercy. Therefore it is said, "vancha-kalpa-tarubhyas ca, krpa-sindhubhya eva ca, patitanam pavanebhyo, vaisnavebhyo namo namah"(I offer my respectful obeisances unto the Vaishnava devotees of the Lord. They are just like desire trees and can fulfill the desires of everyone, and they are full of compassion for the fallen conditioned souls.)