A man Buying food with Payment to be Made Later, and the Seller Asking for something as Collateral for this Price

It was narrated that 'Aishah said:

"The Messenger of Allah bought some food from a Jew with payment to be made later, and he put his shield in pledge for that."

أَخْبَرَنِي مُحَمَّدُ بْنُ آدَمَ، عَنْ حَفْصِ بْنِ غِيَاثٍ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتِ اشْتَرَى رَسُولُ اللَّهِ صلى الله عليه وسلم مِنْ يَهُودِيٍّ طَعَامًا إِلَى أَجَلٍ وَرَهَنَهُ دِرْعَهُ ‏.‏