We classify all <inline-formula> <tex-math notation="LaTeX">q </tex-math></inline-formula>-ary <inline-formula> <tex-math notation="LaTeX">\Delta </tex-math></inline-formula>-divisible linear codes which are spanned by codewords of weight <inline-formula> <tex-math notation="LaTeX">\Delta </tex-math></inline-formula>. The basic building blocks are the simplex codes, and for <inline-formula> <tex-math notation="LaTeX">q=2 </tex-math></inline-formula> additionally the first order Reed-Muller codes and the parity check codes. This generalizes a result of Pless and Sloane, where the binary self-orthogonal codes spanned by codewords of weight 4 have been classified, which is the case <inline-formula> <tex-math notation="LaTeX">q=2 </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\Delta =4 </tex-math></inline-formula> of our classification. As an application, we give an alternative proof of a theorem of Liu on binary <inline-formula> <tex-math notation="LaTeX">\Delta </tex-math></inline-formula>-divisible codes of length <inline-formula> <tex-math notation="LaTeX">4\Delta </tex-math></inline-formula> in the projective case.