The Shaykh Salih al-Fawzaan (rahimahullaah) said:
The source in the interpretation of the Quran – as the scholars mentioned – (revolve around) Five things:
The First Source: Interpretation of the Quran with the Quran, because the Quran, some of it explains the other.
The Second Source: Interpretation of the Quran with the words of the Messenger (Sallallaahu alayhi wasallam), because he is the indicator (to its clarification).
The Third Source: Interpretation of the Quran with the interpretation of the companions, because they are students of the Messenger (Sallallaahu alayhi wasallam).
The Fourth Source: Some scholars interpret the Quran with the words of the Taabi’een, because they took from companions and they knew the meanings of the Quran, better than others.
The Fifth Source: Its interpretation with the Arabic language, because it came down with it.
Source:
Al-Mulakhas fee Sharh Kitaabit-Tawheed, Pg: 154