Sura Ṣād 38:44

وَخُذْ بِيَدِكَ ضِغْثًا فَٱضْرِب بِّهِۦ وَلَا تَحْنَثْ إِنَّا وَجَدْنَٰهُ صَابِرًا نِّعْمَ ٱلْعَبْدُ إِنَّهُۥٓ أَوَّابٌ

wa-khudh bi-yadika ḍighthan fa-iḍrib bbihi wa-lā taḥnath innā wajadnāhu ṣābiran nniʿma l-ʿabdu innahu awwābun

"And take in thy hand a little grass, and strike therewith: and break not (thy oath)." Truly We found him full of patience and constancy. How excellent in Our service! ever did he turn (to Us)!