Seven appears frequently in the story of Samson, tempting us to place significance on every occurrence of the number in his story. Here is the first occurrence,

Then Samson said to them, “Let me pose a riddle to you. If you can correctly solve and explain it to me within the seven days of the feast, then I will give you thirty linen garments and thirty changes of clothing” (Judges 14.12).

Samson spoke those words, but he merely accommodated the seven days of the feast of the Philistines! Seven will show up with meaning later in his story, but I do not believe there is any significance, at least biblically and spiritually, in this passage, although it may have meant something to the Philistines.