"As they were sitting there, the Blessed One said to them, "Sakyans, do you observe the eight-factored uposatha?"
"Sometimes we do, lord, and sometimes we don't."
"It's no gain for you, Sakyans. It's ill-gotten, that in this life so endangered by grief, in this life so endangered by death, you sometimes observe the eight-factored uposatha and sometimes don't..."
As for Those seeking for meditation, Vipassana, a simply prerequisite, useless if not willing let go of sensual pleasures.