diṣṭyā saṁsāra-cakre ’smin
upalabdho bhavān adya
diṣṭyā—it is also by great fortune; saṁsāra-cakre asmin—in this world of birth and death; vartamānaḥ—although I was existing; punaḥ-bhavaḥ—my meeting with you is just like another birth; upalabdhaḥ—being obtained by me; bhavān—you; adya—today; durlabham—although it was never to happen; priya-darśanam—to see you again, my very dear friend and brother.
It is also by good fortune that I am seeing you. Having obtained this opportunity, I feel as if I have taken birth again. Even though one is present in this world, to meet with intimate friends and dear relatives in this material world is extremely difficult.
Vasudeva had been imprisoned by Kaṁsa, and therefore, although present in Mathurā, he was unable to see Nanda Mahārāja for many years. Therefore when they met again, Vasudeva considered this meeting to be another birth.
Link to this page: https://prabhupadabooks.com/sb/10/5/24