When death is mentioned and I say, for example, "God forbid," is there a sin in that?

Death is a calamity that Allah described as such in the Qur’an. Fear of it is natural and innate, and there is no harm in seeking refuge from it. However, this does not delay an appointed term. What is obligatory is to prepare for death, remember it, and increase in good deeds before it is too late. The Prophet, peace and blessings be upon him, encouraged the remembrance of death.