Can you say kolay gelsi for a 3rd person?

Thank You

My understanding is "kolay gelsin" is an expression used that means "may it come easy". It is only said directly to the person working, to suggest that hopefully their work has no difficulties, or goes easily for them. The ´sin´ ending is not related to the second person singular suffix in this form. It is similar to "geçmiş olsun" and "kutlu olsun" in form.

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You can say "ona kolay gelsin".