صَبَنْتِ الْكَأْسَ عَنَّا أُمَّ عَمْرٍو وَكَانَ الْكَأْسُ مَجْرَاهَا الْيَمِينَا
O Umm ʿAmr, you turned the cup away from us, although the customary course of the cup was to the right.
Ṣabanti means “you withheld” or “diverted”; al-kaʾs may denote the cup and its contents. Majrāhā means its usual course.
The speaker invokes the rightward circulation of the cup to protest being passed over. This is an appeal to a practice within the poetic gathering, not a general religious rule.