Are the marks of prostration the indentation on the forehead?

Question : Also, the hadith of Khawlah mentioned earlier, which they know by the marks of prostration. If someone were to say that the marks of prostration are the indentation that appears on the forehead, or sometimes on the palms,

Answer : Yes, that would be incorrect. Because these depend on the condition of a person's skin and the surface on which he prostrates. If a person prostrates on rough gravel, his forehead is affected quickly. Likewise, if his skin is not tough. If his skin were tough and he prostrated on something like his carpet now, he could remain for a thousand years and not be affected.