«أَقْبَلُ مِنْكَ عَلَى أَنْ أُلَازِمَهُ لَيْلَتِي وَيَرْعَاهُ إِنْسَانُ مُقْلَتِي»
I agree provided he stays beside me tonight, watched by the pupil of my eye.
Ulāzimahu means to remain close to someone; insān muqlatī is the pupil of the eye. The figurative watchman inside the eye conveys unbroken surveillance. The elder appears to be protecting his security until the balance arrives. Its real narrative function becomes clearer after the recognition scene.