Mughirah (may Allah have mercy on him) said: Umar bin Abd al-Aziz (may Allah have mercy on him) had companions of the night whom he would consult about the people's affairs that were brought before him, and the sign between him and them, when he wanted them to rise and leave, was that he would say: When you wish.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20309