21. Retirement of subscriber
When a subscriber-
(a) has proceeded on leave preparatory to retirement or if he is employed in a vacation department on leave preparatory to retirement combined with vacation, or
(b) while on leave, has been permitted to retire or been declared by a competent medical authority to be unfit for further service the amount standing to his credit in the fund shall, upon application made by him in that behalf to the accounts officer, become payable to the subscriber:
PROVIDED that the subscriber, if he returns to duty, shall, if required to do so by the director general, repay the fund, for credit to his account, the amount paid to him from the fund in pursuance of this rule with interest thereon at the rate provided in rule 13 in cash or securities by installments or otherwise, by recovery from his emoluments or otherwise, as may be directed by the authority competent to sanction an advance for the grant of which special reasons are required under sub-rule (2) of rule 14.