It was recited وَهَنَ with the three vowel markings. He mentioned the bone because it is the pillar of the body, and through it, the body stands firm; it is the foundation of its construction. If it weakens, it collapses and its strength falls apart. This is because it is the strongest and most solid part of it. If it weakens, what is behind it is even weaker. He used the singular form because the singular indicates the meaning of the genus. He intends to show that this genus, which is the pillar and support, and the strongest component of the body, has been weakened. If he had used the plural, it would have indicated another meaning, which is that not some of his bones have weakened, but all of them. The merging of the 's' into the 'sh' is attributed to Abu Amr. He compared gray hair to the flame of fire in its whiteness, brightness, and its spreading in the hair, and its pervasive effect on it, like the fire's ignition. Then he presented it as a metaphor, attributing the ignition to the place of the hair and its origin, which is the head. He mentioned the gray hair distinctly and did not add 'the head,' relying on the listener's knowledge that it is the head of Zakariya. Thus, this phrase became clear and was confirmed by its eloquence. He sought to Allah by what has preceded him of responsiveness. And it is reported from some that a needy person asked him and said: 'I am the one you did good to at such and such time.' He said: 'Welcome to the one who sought us through us,' and he fulfilled his need.