It is not permissible to sell gold for gold except hand-to-hand

Question: There is a brother asking about the matter of buying gold. He says: If a person goes to buy gold, and the value of what he buys is 1000 pounds (one thousand pounds), and he has only 950 pounds with him, is it permissible for him to take the gold and return the fifty pounds later, or should he leave the gold until he brings the remaining amount? Or is there riba in that? And is it permissible to defer the remaining amount for a period? Knowing that the price of gold is not fixed? I ask Allah, then you, to clarify and detail this matter; for there is much disagreement in the issues of gold. May Allah reward you with good.

Answer: Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. After that:
The answer to the question mentioned is: It is not permissible to sell gold for gold except hand-to-hand, like for like, equal in every respect, as the authentic hadiths from the Messenger of Allah (peace and blessings be upon him) in the two Sahihs and others have established. Whoever says otherwise, his statement is invalid and it is not permissible to rely on it, because it contradicts the authentic hadiths and the consensus of the scholars of knowledge. And may Allah send prayers and peace upon our Prophet Muhammad, his family, and his Companions.
'Abd al-'Aziz ibn 'Abdullah ibn Baz
The Grand Mufti of the Kingdom of Saudi Arabia