Volume 3, Book 34, Number 282:
Narrated 'Aisha (radiallaahu `anhaa):
The Prophet (sallallaahu `alayhi wasallam) purchased food grains from a Jew on credit and mortgaged his iron armor to him.
Volume 3, Book 34, Number 283:
Anas (radiallaahu `anhu) went to the Prophet (sallallaahu `alayhi wasallam) with barley bread having some dissolved fat on it. The Prophet (sallallaahu `alayhi wasallam) had mortgaged his armor to a Jew in Medina and took from him some barley for his family. Anas (radiallaahu `anhu) heard him saying, "The household of Muhammad (sallallaahu `alayhi wasallam) did not possess even a single Sa' of wheat or food grains for the evening meal, although he has nine wives to look after."
Mortgage: convey (a property) to a creditor as security on a loan.
It is neither the taking out of a loan nor a mortgage which by itself is unlawful or prohibited in Islam; what is unconditionally and specifically prohibited and absolutely unlawful in the Sight of Allah is the ‘interest’ element in the loan or the mortgage.
Thus if one takes out an interest-free mortgage on their house or property, such a transaction would be absolutely lawful in the Sight of Shariah Law.
This is the general and overall ruling. Further details will come in the future inshaAllah.