Dan 6:10

6:10 down on his knees. Standing may have been a regular posture in prayer (1 Chr. 23:30; Neh. 9:2–5), while kneeling, a mark of humility, occurred in circumstances of particular solemnity (1 Kin. 8:54; Ezra 9:5; Ps. 95:6; Luke 22:41; Acts 7:60; 9:40).

as he had done previously. Evidently Daniel’s prayer habits were public knowledge.