If the leave without pay for four months or whatever duration is approved one based on the emergencies to the satisfaction of the employer, the gap will not be treated as break in service. There is no need to make him rejoin when he resumes service. Since during his lay days no salary is paid, the PF and ESI records show these periods as non contributory periods. Obviously, if he leaves after completion of the eligible service for payment of gratuity, (ie, five years) the year in which he had taken UNCONDITIONAL APPROVED leave without pay will be treated as countable service. On the other hand, if the leave is approved on a condition that the period of leave will not be counted for the purpose of calculation of gratuity in future, then he will not be entitled to get that year included in the service provided during the remaining days in that year in which he had taken LOP he had not worked for 240 days inclusive of paid leaves and holidays.
Regards,
Madhu.T.K