How to refuse to work
The most frequent form of refusal is the silent one. As it becomes clear that this particular candidate is being eliminated, he simply ceases to communicate with him. If he initiates contact himself, politely explain that, unfortunately for him, another candidate turned out to be more suitable.
As a refusal can often be interpreted and the phrase "we'll call you" instead of moving to the procedure for formalizing relations after the final stage of selection.
Less common is the option of refusal, when all applicants who have not been selected, or those who have dropped out in the final stages (this is more common, since the total number of all who respond to the vacancy is too high) is sent (but not spam: ) message that the preference is given to another.
Usually this is the standard form: the candidate is thanked for attention to the company, regretfully informs that the choice is not in his favor, and wish success.
In this "refusal letter", the phrase can be used that the candidate's candidacy can be considered by the company in the future. Everyone understands that it does not oblige to anything and basically does not mean anything, it's not more than a courtesy.
However, it can be otherwise. Even when the choice is made, there is no complete certainty that the selected bidder will get accustomed to the company. In this case, anyone who professionally recruits personnel keeps a reserve from other applicants. And the phrase this may mean that the screened candidate is included there.
But even this does not guarantee anything.
So the question, whether to use this way to sweeten the pill or not, remains at the discretion of everyone.