time enough

There'll be time enough to relax when you've finished your work.

participant (in something)

participator; a person who is taking part in an activity or event

He has been an active participant in the discussion.

oath

solemn declaration naming God etc. as witness

to take/swear an oath of allegiance

All members had to swear a solemn oath never to reveal the secrets of the organization.

You are bound by oath to tell the truth.