In Daniel 10 Daniel had been in mourning/fasting for 3 weeks, he was having visions and prophecies of the future.
Finally, Gabriel came to him in a vision and told him (verses 12-14):
Then he said, “Don’t be afraid, Daniel. Since the first day you began to pray for understanding and to humble yourself before your God, your request has been heard in heaven. I have come in answer to your prayer. But for twenty-one days the spirit prince of the kingdom of Persia blocked my way. Then Michael, one of the archangels, came to help me, and I left him there with the spirit prince of the kingdom of Persia. Now I am here to explain what will happen to your people in the future, for this vision concerns a time yet to come.”
Daniel’s concerns were heard when he first started to pray, and Gabriel was sent to answer, but the ‘spirit prince’ blocked him from answering, and the Archangel had to come and assist, all the while Daniel was fasting. Gabriel finally broke through and after 21 days, Gabriel finally arrived to give Daniel the message from the Lord. And Micheal had to stay so Gabriel could go…This sounds to me like some heavy spirit warfare…even for the Old Testament..