جَالِسِ الْحَسَنَ أَوِ ابْنَ سِيرِينَ
You may sit with al-Ḥasan or Ibn Sīrīn.
A real command directs the hearer to bring about an action; permission makes a course of action allowable. The same form may serve either purpose. The decisive issue is whether the speaker requires action or simply grants a choice.
If someone asks, “Whose gathering may I join?”, the response jālis al-Ḥasana aw ibna Sīrīn naturally grants permission. If a teacher assigns one gathering as required classwork, a different force is possible. Context determines the reading.