Daniel 10:4

Daniel had gone to the Tigris (Hiddekel, AV) River, perhaps to pray for the exiles who had returned, and he had probably gone there with other godly Jews. Passover and the Feast of Unleavened Bread fell on the fourteenth through the twenty-first days of the first month. The Jews did not observe these festivals in captivity as they had formerly in their own land. Three days after these important memorial days, God gave Daniel a vision that he alone saw (cf. Daniel 12:5).