For example the evaporation of water and its disappearance in the atmosphere; the transformation of solid matter into fluid or gas (steam); or in nuclear fission the transformation of matter into energy. Likewise we also observe in the world a movement in the other direction namely from the invisible to the visible. Gases become fluid evaporated water is transformed into drops of rain or snow or even hail and energy into matter. Similarly intangible thoughts and meanings in our minds can appear in the tangible form of letters and words in essays and books.
In an analogous way invisible beings like angels jinn and other spirit entities are clothed in some material substance such as air or ether and then become visible. If God wills. He allows them to take on a form when they utter any of God's Names which functions like a key or visa enabling them to take on form and they become visible in the world. If they attempt to take on a visible form without God's permission in reliance on their abilities they are torn into pieces and perish.
We read in the Holy Book (19:17) that the spirit God sent to Mary and whom Muslim scholars have concluded to the Archangel Gabriel appeared before her as a human being. When Gabriel came to the Messenger Muhammad with Revelation or God's Messages he rarely appeared in his original form but usually came in the form of either a warrior or a traveler or a Companion called Dihya.
Like angels and Jinn. Satan (who belongs to the jinn) can also appear in different forms. It is narrated that before the Battle of Badr he appeared to the leaders of the Quraysh in the form of on old man from Najd and gave them some advice. Likewise a Companion who was keeping guard of war spoils caught him trying to harm the spoils. He entreated the Companion to release him which he did. However when this took place the third time the Companion attempted to take him to God's Messenger but Satan appealed: . Release me and I will tell you that by which you can be secure against me.. The Companion asked what that was. Satan replied that it was the Verse of the Throne (2:255). When informed of the event. God's Messenger commented: 'That wicked one is a liar but on that occasion he told the truth.'
In the Holy Book a party of jinn listened to God's Messenger reciting the Holy Book and when they returned to their people they said: "Our people! Surely we listened to a Book which has been revealed after Moses and affirms what precedes it and which guides to right and to the Straight Path (46:30). " The Chapter continues with their impressions of or remarks on what they listened to. There are also Traditions which tell us that the Messenger recited to them from the Holy Book and preached to them his Message.
Jinn can also appear in the forms of different animals like snakes scorpions cattle donkeys and birds. When the Messenger took the oath of allegiance from them in the Valley he wanted them to appear to his Companions either in their own form or in other agreeable forms not in the forms of harmful animals like dogs and scorpions. He also warned his Companions saying: When you see any vermin in your house say to it three times: . For God's sake leave here!. For it may be from your Jinn friends. If it does not leave it is not from jinn. Then you are permitted to kill it if it is harmful. The jinn who gave allegiance to God's Messenger promised him: . If your Companions recite "In the Name of God the All-Merciful the All-Com-passionat" before anything they do and cover all their dishes we will touch neither their food nor their drink.. We do not know how they eat of our foods or drink of our beverages. Another Tradition says: [When you have relieved yourselves] do not clean yourselves with bones and dried pieces of dung for they are among the foods of your Jinn brothers.