The word ‘Mawla’ in Arabic language is derived from the same word as the word “Authority” and it also refers to friendship as well. According to the Qur’an, God is believers’ ‘Mawla’ and He is the best ‘Mawla’, which implies both the meanings; that is, believers love God and follow Him as well. However, ‘Mawla’ has both positive and negative meanings and the Qur’an has named bad ‘Mawlas’ (Leaders) as well:

"If they refuse, be sure that Allah is your Protector - the best to protect and the best to help" (Surat Al-Anfal , Verse 40). "They call on one whose hurt is nearer than his profit: evil, indeed, is the patron, and evil the companion (or help)!" (Surat Al-Hajj, verse 13).

Therefore, the words ‘Imam’ and ‘Mawla’ have both a very general meaning and in order to understand their real meanings, we should take into consideration their usage in a sentence or the way they are expressed.

Selection of Appropriate Word by Prophet Muhammad (PBUH)

The holy Prophet Muhammad (PBUH) in Al-Ghadir Khumm used the word ‘Mawla’ and not ‘Imam’. In order to understand the real meaning of this word, we can rely on some evidence: one is the great Muslim masses who assembled there on the order of Prophet Muhammad (PBUH) and secondly the people’s behavior and their confessions after Al-Ghadir Event.

Here, we’d like to understand the real meaning of ‘Mawla’ according to what Prophet Muhammad (PBUH) himself said. Before mentioning the famous sentence, “For whosoever I am Leader (mawla), Ali is his mawla,” the Holy Prophet says: "Do I not have more right over the believers than what they have over themselves?"

All the Muslims together answered:

“Yes! Messenger of God, you have more right over us than what we have over ourselves.”

In fact, here, by reminding the believers of one part of Surah Al-Ahzab, Verse 6, Prophet Muhammad made them confess that:

"The Prophet is closer to the Believers than their own selves"

Therefore, the believers are always careful to give priority to holy Prophet Muhammad's desire in their financial matters and other issues and in their relations with others. If they are not on the same track with the Holy Prophet's ideas, the believers would immediately prefer his ideas to their own.
Now we can understand that the word 'Mawla' in the sentence of Prophet Muhammad (PBUH) is broader than 'Imam'.

Source: Tebyan