Uninterruptedly, there are tens of narrations related to the Ahl ul-Bayt (a) with regard to the great rewarding and grand credit obtained due to the pilgrimage to the Imams’ shrines.
Amir ul-Mu’minin (a) narrated: We served the Prophet (s), who was visiting us, some of the milk, butter, and dates that Ummu Ayman had given to us. After he had had some, he moved to a corner to offer a prayer. During the last prostration of that prayer, he wept very heavily. As we used to respect and honor him greatly, none of us could ask him. Al-Hussein then approached him and said: “Father, the greatest pleasure that we had ever felt was at these moments when you visit us. But we also felt great sor row when we noticed you weeping. What for are you weeping?” “Son,” answered the Prophet (s), “The angel Gabriel has just come to me to foretell that you all will be killed in different areas of this earth.” “Father,” asked al-Hussein, “What will be the r eward of him who visits us in such different areas?” The Prophet (s) answered: “There will be groups of my umma visiting your tombs for seeking blessings. I engage myself with the pledge that I, on the Day of Resurrection, will come to save them from the horrors of the Hour of Resurrection that they will suffer because of their sins. Allah will surely make Paradise their abode.” ( Bihar ul-Anwar; 22/ 7 (as quoted from Kamil uz-Ziyara and al-Amali) )