Srimad Bhagavatam Canto 09, Chapter 05, Text 20

SB 9.5.20

prito ’smy anugrhito ’smi
 tava bhagavatasya vai
darsana-sparsanalapair
 atithyenatma-medhasa
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Durvasa Muni said: I am very pleased with you, my dear King. At first I thought of you as an ordinary human being and accepted your hospitality, but later I could understand, by my own intelligence, that you are the most exalted devotee of the Lord. Therefore, simply by seeing you, touching your feet and talking with you, I have been pleased and have become obliged to you.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
It is said, vaisnavera kriya mudra vijñeha na bujhaya: even a very intelligent man cannot understand the activities of a pure Vaisnava. Therefore, although Durvasa Muni was a great mystic yogi, he first mistook Maharaja Ambarisa for an ordinary human being and wanted to punish him. Such is the mistaken observation of a Vaisnava. When Durvasa Muni was persecuted by the Sudarsana cakra, however, his intelligence developed. Therefore the word atma-medhasa is used to indicate that by his personal experience he would understand how great a Vaisnava the King was. When Durvasa Muni was chased by the Sudarsana cakra, he wanted to take shelter of Lord Brahma and Lord Siva, and he was even able to go to the spiritual world, meet the Personality of Godhead and talk with Him face to face, yet he was unable to be rescued from the attack of the Sudarsana cakra. Thus he could understand the influence of a Vaisnava by personal experience. Durvasa Muni was certainly a great yogi and a very learned brahmana, but despite his being a real yogi he was unable to understand the influence of a Vaisnava. Therefore it is said, vaisnavera kriya mudra vijñeha na bujhaya: even the most learned person cannot understand the value of a Vaisnava. There is always a possibility for so-called jñanis and yogis to be mistaken when studying the character of a Vaisnava. A Vaisnava can be understood by how much he is favored by the Supreme Personality of Godhead in terms of his inconceivable activities.
Srimad Bhagavatam Canto 09, Chapter 05, Text 19
Srimad Bhagavatam Canto 09, Chapter 05, Text 21