Concept of Three Festivals

שָלוֹש פְעָמִּים ׀ בַשָנָה יֵרָאֶה כָל־זְכוּרְ ךָ אֶת־פְנֵי ׀ יְהוָֹה אֱלֹהֶיךָ בַמָקוֹם אֲשֶר יִּבְחָר בְחַג הַמַצּוֹת וּבְחַג הַשָבֻעוֹת וּבְחַג הַסֻכוֹת וְלֹּא יֵרָאֶה אֶת־פְנֵי יְהוָֹה רֵיקָם( :דברים טז ,טז )

Since the Torah just discussed each of the three festivals, this verse only needed to state שלש פעמים three times, and the meaning would have been understood. Why did the Torah spell out the name of each festival? The apparent redundant mention of each festival’s name is teaching that one is liable for delaying fulfilling his “vows” (offerings and monetary) only after all three festivals have passed.