What is the ruling on money taken from the "Hafiz" program after joining work and before registering with social insurance?

The hesitation and confusion you are experiencing are a sign of your faith. The Messenger of Allah, peace and blessings be upon him, said: "Consult your heart. Righteousness is that with which the soul is tranquil and the heart is at peace. Sin is that which wavers in the soul and causes hesitation in the chest, even if people give you a fatwa (religious verdict) about it." The bonus you received after your employment is not rightfully yours, and you are obligated to return it to the responsible party unless they authorize you to benefit from it. This is based on the Prophet's saying: "Indeed, some men delve into the wealth of Allah without right, and for them is the Fire on the Day of Resurrection." If the responsible party permits you to benefit from it, then you may do so. Otherwise, you are obligated to return it.