Once Prabhupada told me that if a person does not chant Hare Krishna, then his devotional service becomes karma. In other words, his activities become karmic. After all, what’s the difference between what devotees and non-devotees do? The difference is that the holy sound vibration, which keeps us in touch with the Supreme Lord, purifies our activities.
Reference: Memories Anecdotes of a Modern Day Saint – Volume 3 by Siddhanta Dasa
courtesy:- https://www.srilaprabhupadalila.org/read/2354