I wrote this ritual more than a decade ago, so I can’t remember if we used it in this exact form, but I think it’s important to have rituals to mark changes in your group. Just as you welcome new people with initiations and other commitment ceremonies, it makes sense to offer some sort of closure when they leave.
Start with brief explanation of reasons for leaving & reactions from those remaining.
Set up the circle in the usual way for your tradition.
Each covener charges a pebble or other gift with blessings for the leaver.
The leaver stands before the altar and says:
Farewell. I go to follow the path of the Hedge Witch / Hearth Fire / [name of other coven]
(Hedge Witch if working solitary; Hearth Fire if not planning to practice the Craft; name of other coven if joining another coven; if this is a temporary absence, add “for a while”)
The leaver stands before the temple guardian(s) and says:
Hail and Farewell.
The leaver stands before the coven and says:
I will not be walking by the same path as you,
but I will be travelling on the same journey.
I pledge not to reveal the secrets of this coven [coven name],
and always to honour the divine in each one of you. Farewell.
The coveners respond, one by one, giving their pebble/gift and personal words of blessing to the leaver:
I pledge to honour and comfort you, and to help you on your path.
I honour the divine within you. Farewell.
The leaver consecrates a cup of wine and addresses either the gods of the Craft or the patron deities of the coven:
Lady of the Moon, Horned One,
what I do now and henceforth is in your honour.
May I be granted the inner peace and knowledge
that is the measure of one who follows you.
Though I am moving to a different path, I know that you are with me.
The leaver drinks from the cup and turns to the coven:
I pledge this cup to you all in token of Farewell.
All drink from the cup. All coveners say:
Farewell, and blessings on your journey.