Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Taking money from your father without his consent is not permissible.
Answering your question, the Fatwa Center at Islam Q and A, states:
Taking money from your father without his consent is not permissible. The Prophet (peace be upon him) said: “It is not permissible to take the wealth of a Muslim except with his consent.” ( Classed as sahih by al-Albaani).
The son has no right to take anything from his father’s wealth beyond what the father is reasonably required to spend on his maintenance if the father is obliged to spend on his son’s maintenance because the son is poor.
Imam Ibn Muflih said in Al-Furu` (5/595):
“The father is obliged to spend on his son in reasonable terms for what he needs of maintenance, or some of it, and to provide clothing and shelter, if his children are poor.”
Now you have two choices:
1- Telling your father what you did, and he will either forgive you or ask you to pay back the money, and he has the right to do that.
2- Not telling him, especially if you fear that this will cause trouble, such as a dispute or conflict between you and your father, or his loss of trust in you. In that case, you must return the money to him, but it is not essential for you to inform him of that; rather the aim is to return the money to him by any means.
The scholars of the Permanent Committee for Ifta’ were asked about the son taking from his father’s wealth more than the maintenance that the father allowed him to take as needed.
They replied:
“You must return what you saved of money that you took from your father for maintenance, because he allowed you to take according to household needs, but anything surplus that is not included in the permission he gave is not permissible for you to take it.” (Fatawa al-Lajnah ad-Da’imah lil-Ifta’ (21/175)
Almighty Allah knows best.
Source: www.islamqa.info