You cannot work for two different people, organizations, or purposes in good faith, because you will end up favoring one over the other.

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No man can serve two masters A man with two employers cannot be faithful to both. Nor can a man support two conflicting causes. The source is Matthew, vi, 24: ‘No man can serve two masters; for either he will hate the one and love the other; or else he will hold to the one, and despite the other. Ye cannot serve God and mammon.’