They are the need for food, drink, sleep, rest, marriage, urination, defecation, and other needs from which no human is free. If we lift these constraints from our Masters, then do you think their bodies are like ours?!
Our Master Amir Al-Mouminine (May His Glory be Mighty) said: "O Salmān, when our dead one dies, he has not died; our slain one has not been slain; and when our absent one is absent, he has not been absent."1
Dāwūd ibn Kathīr al-Raqqī (Peace be upon him) said: "Samāʿa ibn Mihrān and I entered upon our Master al-Ṣādiq (May His Glory be Mighty), and before him was a man from Khurāsān who had brought him money. He said to him: 'O Khurāsānī, you withhold your very selves from us, yet you are generous with your wealth, as if we are in need of it. God only desires to remove all impurity from you, O People of the Household, purify you with a thorough purification, remove from you the heat of iron, suffice you, and write you down among His loyal friends, along with the chosen elite of His creation.'"2
Our Master al-Riḍā (May His Glory be Mighty) said in describing the Imam: "He sees behind him just as he sees in front of him, he has no shadow, and when he falls to the ground from his mother's belly, he falls on his palms."3
He has no shadow.
Why does he have no shadow?
And what is a shadow?
The shadow is the dark area that results from any material body obstructing light from its various sources, thus producing a dark area on another body in the shape of the body that obstructed the light.
If we delve deeper into the subject of the shadow, its characteristics, and its effect, and link them to the fact that the Imam has no shadow, deep-thinking researchers would find many indications. However, we will now point only to the necessary point, which is that a shadow is formed by a material body obstructing light. This means that the Imam's body is non-material like the rest of the bodies to produce a shadow like them, or at the very least, that his nature is different.