You need to read the whole passage for context. This is not saying to obey traditions over commandments of God. Sunday worship was never a tradition or taught in scripture nor is it a commandment of God.
1 Thes 2:13 But we are bound to give thanks to God always for you, brethren beloved by the Lord, because God from the beginning chose you for salvation through sanctification by the Spirit and belief in the truth, 14 to which He called you by our gospel, for the obtaining of the glory of our Lord Jesus Christ. 15 Therefore, brethren, stand fast and hold the traditions which you were taught, whether by word or our epistle.
Jesus on the other hand said very specifically to not obey traditions over commandments of God which is considered worshipping in vain according to Jesus. Mat 15:3-9
3 He answered and said to them, “Why do you also transgress the commandment of God because of your tradition? 4 For God commanded, saying, ‘Honor your father and your mother’; and, ‘He who curses father or mother, let him be put to death.’ 5 But you say, ‘Whoever says to his father or mother, “Whatever profit you might have received from me is a gift to God”— 6 then he need not honor his father or mother.’ Thus you have made the commandment of God of no effect by your tradition. 7 Hypocrites! Well did Isaiah prophesy about you, saying:
8 ‘These people draw near to Me with their mouth,
And honor Me with their lips,
But their heart is far from Me.
9 And in vain they worship Me,
Teaching as doctrines the commandments of men.’ ”