1. To obey the command of Allah Almighty.
Allah Almighty says: 'O you who believe! Obey Allah and His Messenger, and do not turn away from him when you hear.' (Surah al-Anfal verse 20). This kind of meaning verse is repeated in the Quran.
2. To earn the love of Allah Taala.
'Say, “If you love Allah, then follow me, and Allah will love you, and will forgive you your sins.” Allah is Forgiving and Merciful.' (Surah Ali Imran verse 31)
Hasan Basri (may Allah have mercy on him) said:
"The sign of the servant's love for Allah is to follow the Sunnah of the Prophet (peace and blessings of Allah be upon him)."
3. To compensate for the shortcomings in the fard actions.
4. To avoid being misled by heresy (bidah) and error.
The Messenger of Allah (peace and blessings of Allah be upon him) said: 'I have left two things in you. If you hold them tight, you'll never go wrong. These are the Book of Allah and my Sunnah.'
May Allah help us all to follow the Sunnah of the Messenger of Allah (peace and blessings of Allah be upon him) and to go continually on it!