Life was given me as a favour; I may consequently give it back, when it is no longer so.

[La vie m’a été donnée comme une faveur ; je puis donc la rendre lorsqu’elle ne l’est plus.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689-1755) French political philosopher

Persian Letters [Lettres Persanes], Letter 76, Usbek to Ibben (1721) [tr. Ozell (1760 ed.), No. 77]
    (Source)

(Source (French)). Alternate translations:

Life was given to me as a favour; I may then return it, when it is no more so.
[tr. Floyd (1762)]

Life was given me as a blessing; when it ceases to be so I can give it up.
[tr. Davidson (1891)]

Life was bestowed upon me as a favor; I may then give it back when it is a favor no longer.
[tr. Betts (1897)]

Life has been given to me as a favor, which I can return when it is that no longer.
[tr. Healy (1964)]

Life was given to me as a kind of favor; when it ceases to be that, I can put an end to it.
[tr. MacKenzie (2014)]