Concealing sins and forgiving them in the Hereafter:
Ibn `Umar, may Allah be pleased with him, reported,
“I heard the Messenger of Allah saying: 'Allah The Almighty will bring a believer close to him on the Day of Resurrection, enveloping him in His Mercy and shielding him from the people. Allah will make him confess his sins by saying: `Do you remember (doing) this sin and this sin on such and such a day?' He will reply: `My Lord, I remember.` The slave will think that he is destroyed, but then Allah will say: `I covered it up for you in the worldly life, and I forgive it for you today.` Then the record of his good deeds will be handed to him.”' [Al-Bukhari and Muslim]
Overlooking mistakes or actions done out of forgetfulness:
The Messenger of Allah said: “My nation will not be held accountable for that which they do erroneously, forgetfully or forcefully”.
Trials and disasters are a form of the mercy of Allah The Almighty:
Allah The Almighty sends down His support according to the need of the slave. He sends down patience to coincide with the affliction of the slave, as the Prophet said. One wonders when he sees some people who are greatly afflicted, yet they live their lives normally. This is because Allah The Almighty supports them to the extent they need.
Anas, may Allah be pleased with him, reported that the Messenger of Allah said: “Any Muslim who loses three children before they reach the age of maturity, will be granted Paradise by Allah, The Exalted, out of His Mercy for them.” [Al-Bukhari and Muslim]
`Aa’ishah, may Allah be pleased with her, reported, “I asked the Messenger of Allah about pestilence and he said: 'It is a punishment which Allah sends upon whomsoever He wills, but Allah has made it as a mercy to the believers. Anyone who remains in a town which is plagued with pestilence maintaining patience expecting the reward from Allah, and knowing that nothing will befall him other than what Allah has foreordained for him, he would receive a reward of a martyr.'" [Al-Bukhari]
The mercy of Allah The Almighty in the form of accepting the repentance of His slave:
On the Day of Resurrection, Allah The Almighty will overlook and forgive some sins which He alone is aware of. Many stories inform us that Allah The Almighty will forgive people and individuals despite them committing great sins as in the following narration. Abu Sa`eed Al-Khudri, may Allah be pleased with him, reported that the Messenger of Allah said,
“There was a man from among a nation before you who killed ninety-nine people and then made an inquiry about the most learned person on the earth. He was directed to a monk. He came to him and told him that he had killed ninety-nine people and asked him if there was any chance for his repentance to be accepted. He replied in the negative and the man killed him also completing one hundred.
"He then asked about the most learned man in the earth. He was directed to a scholar. He told him that he had killed one hundred people and asked him if there was any chance for his repentance to be accepted. He replied in the affirmative and asked, 'Who stands between you and repentance? Go to such and such land; there (you will find) people devoted to prayer and worship of Allah, join them in worship, and do not come back to your land because it is an evil place.' So he went away and hardly had he covered half the distance when death overtook him; and there was a dispute between the angels of mercy and the angels of torment. The angels of mercy pleaded, 'This man has come with a repenting heart to Allah,' and the angels of punishment argued, 'He never did a virtuous deed in his life.'
"Then there appeared another angel in the form of a human being and the contending angels agreed to make him arbiter between them. He said, `Measure the distance between the two lands. He will be considered belonging to the land to which he is nearer.` They measured and found him closer to the land (of piety) where he intended to go, and so the angels of mercy collected his soul.” [Al-Bukhari and Muslim]
Note that this man did not perform any good deed after having killed one hundred souls, yet Allah The Almighty forgave him, how can we despair of His Mercy?