The Center of Happiness and the address of prosperity (success).

"وَأَطِيعُوااللَّهَ وَأَطِيعُوا الرَّسُولَ" (At-Taghabun 64:12)

أي: في امتثال أمرهما، واجتناب نهيهما، فإن طاعة الله و طاعة رسوله مدار السعادة، و عنوان الفلاح.
من تفسير الشيخ السعدي

"Obey Allah and Obey the Messenger" [64:12] which is: in obeying their Command, Avoiding their prohibition, For Indeed the Obedience to Allah and Obedience to His Messenger is the center of Happiness and the address of prosperity (success).

From the Tafseer of Shaykh As-Sa'dee.