What is meant by the "abandonment" mentioned in the Hadith: "It is not lawful for a Muslim to abandon his brother for more than three nights," and is the lack of communication with acquaintances for more than three days considered abandonment, especially if communication occurs every two months?

The forbidden abandonment (hajr) mentioned in the Hadith refers to the intention of severing ties, turning away from a Muslim, and refraining from greeting him upon meeting. It does not refer to the inability to meet with a brother or acquaintances due to busyness or distance. Ibn Battal stated in his commentary on Sahih al-Bukhari that the forbidden abandonment is when a man stops speaking to his brother despite their frequent encounters and gatherings, and each turns away from the other in estrangement, and he ceases to greet him. Not meeting due to a brother being in another town because of distance is not included in the forbidden abandonment.