Then Daniel answered and said before the king, Let your gifts be to yourself, and give your rewards to another; yet I will read the writing unto the king, and make known to him the interpretation.
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Aquinas Study Bible
Daniel was not in the habit of selling divine things, or taking payment from human beings for the divine mysteries; so he was willing to give him knowledge of the unknown without charge. (Theodoret of Cyrus)
We should follow the example of a man like Daniel, who despised the honor and gifts of a king, and who without any reward even in that early day followed the Gospel injunction: "Freely have ye received, freely give." And besides, when one is announcing sad tidings, it is unbecoming for him willingly to accept gifts.