What is the ruling on designing a drawing for a Christian priest's home library, most of its books being religious?

If it is highly probable that the priest will use the library shelves to hold books of disbelief (kufr), then it is not permissible to assist him by designing or manufacturing them, due to the aid it provides to evil. Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." The dominance of probability (ghalabat al-dhann) is considered by scholars to take the ruling of certainty.