Imaam al-Shaafi'i (may Allaah have mercy on him) said:
He who learns hadith his evidence becomes strong.
This is one of the secrets when it comes to reaching the right decision in regards to Islamic legislation.
You must learn the hadith and its sciences. You must master them.
When the Qur'aan was revealed, the Companions (may Allaah be pleased with them) did not make their own interpretations of the Verses.
They learned from the Messenger of Allaah (sallallaahu alayhi wa sallam).
His teachings are present in the 'ahadith. You must learn the authentic 'ahadith to know what he (sallallaahu alayhi wa sallam) said and did.
You cannot be a scholar unless you master the science of hadith.