Why did he say "you will tell me the seven days of feasting"?
Malbim: You must tell during the [Stam] "Yemei ha'Mishteh" (the days after the Nisu'in). He told the riddle at the beginning of the days of feasting before the Nisu'in.
What are Sadinim?
Radak: They are linen sheets on which one sleeps at night, or 1 wears during the day.
Perhaps the sheets can also be worn during the day. If they were only for sleeping at night, how did Shimshon take them from the 30 men he killed (verse 19)? However, some say that he gave only the outfits; refer to 14:19:3:1,3 and the note there. (PF)
Rashi there brings from Menachem that they are scarves, like in Yeshayah 3:22, but points out that Yonason distinguished them.
