Loving for the sake of Allaah and hating for his sake

What are the controls for loving for the sake of Allaah and hating for the sake of Allaah? Is it obligatory upon me when I love someone for the sake of Allaah to tell him that I love them?

People of knowledge have stipulated a rule to define loving for the sake of Allah and hating for the sake of Allaah. These parameters will not leave any doubt in the mind of a person that is love for the sake of Allaah which will increase with further clarity, nor reduce if neglected. However, without clarification this is a big issue. Many people are unable to do this. It is for this reason that Ibn ‘Abbaas (may Allah be pleased with him) said during the 1st century of Islam during the period of the prophetic Companions and the senior Successors, ‘Nowadays brotherhood of people is connected to worldly affairs’ (Tazeem qadr al-Salaah, 396). By this he meant the majority of people. There are those that can achieve this, however, during the 1st century there were many who had sincere brotherly love, but thereafter it reduced until it became minimal or very rare ( not increasing or decreasing because of some short term disagreements). This is much like the hadeeth ‘None of you can be believers until you love for your brother what you love for yourself’ (Al-Bukhaary, 13). Even to the extent some scholars said that this occurring is not possible. On the other hand, a large group of scholars and commentators said this is possible for a person who has a righteous heart.
When a person loves someone for the sake of Allaah, the instruction from the Prophet ﷺ was that the person should inform him. Hence, it is laudable to inform such a person. However, it is not obligatory to do so, in the sense that failure to do so will entail being sinful. If he has informed him then there is no doubt that he has carried out the instructions of the Prophet ﷺ and if he has not then there is no sin upon him. However, a person should be eager to do so in order to spread love between individuals in society.