I too saw what you saw in the Scriptures, probably about the same time even! But, what is interesting is it's not the same verse, but it has the same numbers: Chapter 2 verse 3! Check out Malachi 2:3, to me it is even clearer than the Habakkuk 2:3 verse you used. I too had been looking as to what feast was being spoken of. Thanks for taking the time to do the research, I too agree - Pentecost. Here is the verse:

(Malachi 2:3 KJV) "Behold, I will corrupt your seed, and spread dung upon your faces, even the dung of your solemn feasts; and one shall take you away with it."

YBIC, John Nelson