网友的句子来自《新牛津英汉双解大词典》。

句中的 stop 意思是“总是”“老是”“停留于”(相当于系动词)：

He said I mustn't stop barefooted, so I had to buy a pair of new shoes.

他说我不能老光着脚，因此我不得不去买了一双新鞋。

 barefooted 是形容词或副词，意思是“赤脚的（地）”。

He said I mustn’t stop barefooted, so I had to buy a pair of new shoes.

他说我不能光着脚停下来，所以我不得不买一双新鞋。 

备注：barefooted  为形容词. 意思是:  赤脚的;光着脚的。

Some of them were barefooted in this cold weather.  

有些人在这寒冷的天气里还光着脚。

He said that I mustn’t stop barefooted, so I had to buy a pair of new shoes.

=He said that I can't/mustn't be  barefooted when I stop, so I had to buy a pair of new shoes.

备注：形容词作状语表示谓语动词动作发生时主语所处的状态，副词作状语表示谓语动作发生的方式。