Employee liable for making purchases on a company's name after resigning

Please advise who is responsible in the following scenario:

Ahmad gave permission for Ilyaas (his employee) to purchase on his company's name from ABC stores. This carried on for a whole year where he would purchase on behalf of Ahmad's company and payment for the goods would be done 60 days later, as per agreement with ABC stores.

However, without ABC stores knowing, Ilyaas resigned from Ahmad's store. In that month after he resigned, he was still making purchases on Ahmad's name and when the time came for payment, Ahmad refuses to pay as the purchases made in that period were not authorised by him, nor was Ilyaas employed by him, nor did he receive any goods. Ilyaas no longer comes to ABC stores and cannot be reached or found.

Who is liable for the goods in this situation?