These things cannot by lightly passed over ...

“And now, my dearly beloved brethren and sisters, let me assure you that these are principles in relation to the dead and the living that cannot be lightly passed over, as pertaining to our salvation. For their salvation is necessary and essential to our salvation, as Paul says concerning the fathers – that they without us cannot be made perfect – neither can we without our dead be made perfect.” D&C 128:15