Which constitutional provision implicitly requires civil servants to maintain political neutrality by placing them under the control of the elected executive?

Article 309: Parliament/State Legislature may regulate recruitment and conditions of service of persons serving Union/States. Subject to this, President/Governor make rules. Civil services (IAS, IPS, etc.) serve under elected governments; expected to implement policies impartially regardless of political affiliation. All India Services Rules, Conduct Rules enforce neutrality. Balance: Professional advice to political masters while maintaining constitutional loyalty over partisan loyalty.