All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
In light of Sharia, the father has an independent financial liability and so does the son. This is supported by the fact that the son doesn`t pay the Zakah for which his father is liable and vice versa. Moreover, as stated in the Quran, in case the son died, the father is entitled to a specific share of his wealth/estate, not all of it, according to scholarly consensus.
"You and your wealth belong to your father" stated in [Al-Musnad vol.11/pp.503], doesn`t mean that the father has real possession of his son`s wealth or that he may dispose of it without the son`s knowledge and approval for this wasn`t approved by any of the scholars.
The true meaning of this Hadith is that if the father was poor and needed to be provided for, then he may take a portion from his son`s wealth that suffices for his basic needs, just as he would take from his own wealth. However, if the son had no wealth but was able to make a living then he is obliged to provide for his father. In addition, this Hadith doesn`t mean that it is lawful for the father to take whatever he wants from his son`s wealth.
Nonetheless, some scholars of Hadith have considered this Hadith "D`aif" (Weak):
Check Al-Shafie`s book {Al-Risala, pp.468}.
Even if we supposed that this Hadith is authentic, the answer is what we have mentioned above. This answer is also supported by the Hadith reported by A`isha (May Allah be pleased with her) who said that the Prophet said: "Your children are Allah`s gift to you. He bestows (children) male or female according to His Will). They and their wealth is yours if you are in need for it." {Related by Al-Hakim in "Al-Mostadrak, vol.22/pp.284"}.
Apparently, this Hadith is conditioned upon the statement {If you are in need for it}. Thus, it isn`t permissible for the rich father to take his son`s wealth as stated in the afore question. Rather, he must repay that loan; however, if he is poor and needed to be provided for then he may take a portion from his son`s wealth that suffices for his needs, even without the consent of the son and this is the meaning intended from the Hadith: "You and your wealth belong to your father."
Al-Menawi said: "The Hadith means that if your father is in need then he is allowed to take a portion from your wealth that suffices for his basics and not that he may take all your wealth since this wasn`t approved by any of the scholars." {Fayd al-Khadeer, vol.5/pp.13}. And Allah The Almighty Knows Best