Al-Matalib al-'Aliyah 4163 — The virtue of the Companions

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he said: "Do not curse or revile the Companions of Muhammad (peace and blessings be upon him), for Allah, the Mighty and Majestic, has commanded (the believers) to seek forgiveness for them, even though He (the Exalted) already knew well that they would soon do certain acts and deeds (under trials and human circumstances, on account of which you would criticise them)."
Imam Ahmad bin Mani' transmitted this narration; it is da'if (weak) because one narrator in its chain is unnamed. However, its meaning is established by this blessed verse of the Holy Qur'an: "And those who came after them say: Our Lord, forgive us and our brothers who preceded us in faith" [Surah al-Hashr: 10].