The answer is: He felt ill and weak

Daniel 10:8

Daniel's reaction of feeling ill and weak at the vision by the river Hiddekel unveils a rich tapestry of emotional and spiritual experience found throughout the Book of Daniel. This moment serves as a vivid reminder of the weighty impact that visions and revelations can bear on the human soul. Imagine standing by the banks of a shimmering river, sometimes symbolic of life-giving forces— yet within the current of that moment, Daniel was overwhelmed, reinforcing the idea that spiritual experiences can often leave us both enlightened and uneasy.

What's intriguing about Daniel's specific affliction is that it mirrors the responses of other biblical figures who encountered divine revelations. For instance, when the prophet Isaiah saw his vision of the Lord seated on His throne, he felt undone—truly a common response when humans catch a glimpse of the within-the-veil ineffable divine. It underscores our frail humanity, showing that being touched by the divine often carries a heavy weight.

The river Hiddekel, known today as the Tigris, connects to the wider theme of God’s presence, often marked in the natural world. It serves as a temporal backdrop for timeless truths. Additionally, it's noteworthy how such physical reactions in the face of spiritual visions illustrate the depth of connection between the sacred and the earthly, echoing throughout the history of transcendent encounters be they with prophets, sages, or deeply reflective individuals through the ages. Much like Daniel, many would say that true understanding of the divine can indeed be both awe-inspiring and utterly humbling.