What is the most appropriate source of recruitment for an organization? Internal or external source of recruitment? And why?

Hi - depends on the nature of profession, if an organisation is having internal sources it can go ahead with it, but if sources are limited, than it has to move out to talk to some recruitment agency to increase the employees as per the demand.....

Hi, Hopefully Rana naseem you are well and enjoying Life.
Now come to the business, Internal Source of recruitment is the way most of the companies prefer to use specially Multinational and Large organizations who know that they have sufficient pool of prospects / talent and it is also low budget exercise and Companies who are medium or small and have insufficient pool of prospects / talent use external sources but external sources have highly resistance of acceptance too.
So keeping in view mentioned scenario, both are equally appropriate source of recruitment