يَكَادُ الۡبَرۡقُ يَخۡطَفُ اَبۡصَارَهُمۡؕ كُلَّمَاۤ اَضَآءَ لَهُمۡ مَّشَوۡا فِيۡهِۙ وَاِذَاۤ اَظۡلَمَ عَلَيۡهِمۡ قَامُوۡاؕ
Every time it lights [the way] for them, they walk therein; but when darkness comes over them, they stand [still].
It refers to those hypocrites who disbelieved completely but had become Muslims merely, to further their worldly interests. The second parable refers to those who were prone to doubt and hesitation or whose faith was weak; who believed in the Truth but not to the extent of exposing themselves to hardships for its sake.
They move a little ahead when circumstances seem favourable, but when either difficulties cloud the horizon, or when they are given directives which run counter to their desires or inherited prejudices, they are seized with alarm and come to a halt.
I hope it is helpful.