«فَقَضَيْنَاهَا لَيْلَةً غَابَتْ شَوَائِبُهَا إِلَى أَنْ شَابَتْ ذَوَائِبُهَا»
We spent a night free of disturbances until its locks of hair turned grey.
Shawāʾib suggests impurities or unpleasant disturbances; dhawāʾib evokes locks of hair. Night is personified as someone whose hair goes white when dawn approaches.
The echo between ghābat / shābat and between shawāʾib / dhawāʾib adds patterned sound. The sound is not a substitute for meaning: it reinforces the unusual image of a delightful night ageing into daylight.
«وَكَمَلَ سُعُودُهَا إِلَى أَنْ انْفَطَرَ عُودُهَا»
The night reached the height of its good fortune, until its course broke off with dawn.
The echo of suʿūduhā / ʿūduhā joins pleasing sound to the close of the scene.