I read somewhere that the Buddha removed his robes then laid down and asked his disciples to look at his body. I am guessing that the Buddha wanted his students and future practitioners to know that even a Buddha's form body is subject to decay and impermanence.
Please share if there are other understandings about this. Thanks.
Well, I think you are right. Even in his old age and death, the Buddha is using himself for part of this teaching that time is short and that we have seize the essence of this life to practice as much as we can. Also the body is a great physical teaching on the degradation of the human body - and this means Impermanence. I think the Buddha just gave one last great teaching on impermanence when he honestly revealed the physical condition of his body to his student to spur them to think deeper about their current state of mind and their attitude.