"And O my people, this is the she-camel of Allah, for you, a sign." Muhammad said: The accusative case (nasb) of (ayah/a sign) is because it is a state (hal).
﴿وَيَا قَوْمِ هَذِهِ نَاقَةُ اللَّهِ لكم آيَة﴾ قَالَ مُحَمَّدٌ: نَصْبُ (آيَةٍ) عَلَى الْحَالِ؛