НА РАДОСТЯХ (РАДОСТИ) collPrepPthese forms onlyadv
thanks to or because of one's elevated mood (on the occasion of a joyful event)
in one's joy (rejoicing)
from sheer joyin celebrationto celebrateelated (, one does sth.).
Обыкновенно или чиновник умирал, или государь - и тогда наследник на радостях прощал долги (Герцен 2). Usually either the official died or the Tsar did, and then in his rejoicing the heir forgave the debts (2a)
«Постой-ка, угощу тебя», - бессвязно бормотала она, доставая из сундука хранившуюся с давнишних пор бутылку самогона. Прохор присел, разгладил усы. «Ты-то выпьешь со мной на радостях?» - спросил он (Шолохов 5). uJust a minute, I've got something here for you..." she mumbled, rummaging in the chest for a bottle of home-brew that she had been keeping for many a long day. Prokhor sat down and stroked his moustache. "You'll have one with me to celebrate, won't you?" he asked (5a).