SB 4.22.7

pṛthur uvāca
aho ācaritaṁ kiṁ me
 maṅgalaṁ maṅgalāyanāḥ
yasya vo darśanaṁ hy āsīd
 durdarśānāṁ ca yogibhiḥ
Synonyms: 
pṛthuḥ uvāca — King Pṛthu spoke; aho — O Lord; ācaritam — practice; kim — what; me — by me; maṅgalam — good fortune; maṅgala-āyanāḥ — O personified good fortune; yasya — by which; vaḥ — your; darśanam — audience; hi — certainly; āsīt — became possible; durdarśānām — visible with great difficulty; ca — also; yogibhiḥ — by great mystic yogīs.
Translation: 
King Pṛthu spoke: My dear great sages, auspiciousness personified, it is very difficult for even the mystic yogīs to see you. Indeed, you are very rarely seen. I do not know what kind of pious activity I performed for you to grace me by appearing before me without difficulty.
Purport: 

When something uncommon happens in one’s progressive spiritual life, it should be understood to be incurred by ajñāta-sukṛti, or pious activities beyond one’s knowledge. To see personally the Supreme Personality of Godhead or His pure devotee is not an ordinary incident. When such things happen, they should be understood to be caused by previous pious activity, as confirmed in Bhagavad-gītā (7.28): yeṣāṁ tv anta-gataṁ pāpaṁ janānāṁ puṇya-karmaṇām. One who is completely freed from all the resultant actions of sinful activities and who is absorbed only in pious activities can engage in devotional service. Although Mahārāja Pṛthu’s life was full of pious activities, he was wondering how his audience with the Kumāras happened. He could not imagine what kind of pious activities he had performed. This is a sign of humility on the part of King Pṛthu, whose life was so full of pious activities that even Lord Viṣṇu came to see him and predicted that the Kumāras would also come.