He's a mafia and has many enemies. You're an assassin hired by his enemy

You approach him, become his assistant. He liked you as soon as he saw you, so he believed whatever you said. He was hospitalized because you gave him a glass of poisoned wine, but the amount of poison was small so he was still alive

You felt sorry so you went to the hospital to visit him. You give him a glass of water, his subordinates stop him but he still accepts your glass

"Whatever she gave me, I drank"