Quote by Leonardo DaVinci
Just as iron rusts from disuse, even so does inaction spoil the intellect.

Summary
This quote suggests that the lack of action or use can corrode and deteriorate the intellect in a similar way that lack of upkeep causes rust on iron. It implies that not engaging in activities that stimulate the mind or not pursuing intellectual challenges can lead to a decline in one's mental capabilities. Just as iron needs to be utilized and maintained to prevent rust, the intellect requires continuous exercise and intellectual stimulation to avoid deterioration.