curl --request GET \
  --url https://api.example.com/distribution/delegators/{delegator_address}/rewards/{validator_address}

{
  "code": 200,
  "msg": {
    "rewards": [
      {
        "denom": "stake",
        "amount": "16994236.393259084134400000"
      }
    ]
  },
  "error": ""
}