Kautilya's Arthashastra 7.16.22

7.16.22

paribhavopaghātakutsātivādāṃś caiṣu na prayuñjīta //

(The king who is desirous of making conquests) should continue in following the same policy towards him, who, among the above kings, is most helpful and keeps the same attitude; should by secret means bring him round who is opposed; should favour the helpful with facilities for giving further help, besides bestowing rewards and honour at all costs upon him; should give relief to him who is under troubles; should receive visitors at their own choice and afford satisfaction to them; should avoid using contemptuous, threatening, defamatory, or harsh words towards them; should like a father protect those who are promised security from fear; should punish the guilty after publishing their guilt; and in order to avoid causing suspicion to the protector, the vassal-king should adopt the procedure of inflicting secret punishments upon offenders.