What is the interpretation of the Prophet's (peace and blessings of Allah be upon him) saying: "They are a people who loved one another for the sake of Allah"?

The Hadith was narrated by Abu Dawud and others, and its wording, on the authority of Umar ibn al-Khattab, states: The Prophet, peace and blessings be upon him, said: "Indeed, among the servants of Allah are people who are neither prophets nor martyrs, but the prophets and martyrs will envy them on the Day of Resurrection due to their status with Allah Almighty." It was asked: "Who are they, O Messenger of Allah?" He said: "They are people who loved each other for the sake of Allah's spirit, without any kinship between them, nor any money they exchanged. By Allah, their faces are light, and they are upon light. They will not fear when people fear, nor grieve when people grieve." And he recited the verse: "Unquestionably, the allies of Allah - no fear will be upon them, nor will they grieve." Al-Albani authenticated it. "By Allah's spirit" was interpreted by Al-Khattabi as the Qur'an, and it was also said to mean pure love for the sake of Allah Almighty.