Celsus next says: “What is the nature of the ichor in the body of the crucified Jesus? Is it 'such as flows in the bodies of the immortal gods?'” He puts this question in a spirit of mockery; but we shall show from the serious narratives of the Gospels, although Celsus may not like it, that it was no mythic and Homeric ichor which flowed from the body of Jesus, but that, after His death, “one of the soldiers with a spear pierced His side, and there came thereout blood and water.
And he that saw it bare record, and his record is true, and he knows that he says the truth.” Now, in other dead bodies the blood congeals, and pure water does not flow forth; but the miraculous feature in the case of the dead body of Jesus was, that around the dead body blood and water flowed forth from the side. But if this Celsus, who, in order to find matter of accusation against Jesus and the Christians, extracts from the Gospel even passages which are incorrectly interpreted, but passes over in silence the evidences of the divinity of Jesus, would listen to divine portents, let him read the Gospel, and see that even the centurion, and they who with him kept watch over Jesus, on seeing the earthquake, and the events that occurred, were greatly afraid, saying, “This man was the Son of God.”
Source: Against Celsus (New Advent)