Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) recited this verse: "Whether you show what is in your hearts or conceal it, Allah will call you to account for it; then He will forgive whom He wills and punish whom He wills" [Surah al-Baqarah: 284], and tears flowed from his eyes. This reached Ibn Abbas (may Allah be pleased with them both), and he said: May Allah forgive Abu Abd al-Rahman (Ibn Umar). By my life, this verse troubled the Muslims before him too, until Allah, the Mighty and Majestic, revealed: "Allah does not burden any soul beyond its capacity; for it is what it has earned, and against it is what it has done" [Surah al-Baqarah: 286]. He said: Whispering (waswasah) is what people have no control over, and Allah has decreed for every soul a recompense according to what it has earned.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10723
Sa'id bin Marjanah narrated: I was with Ibn Umar (may Allah be pleased with them both) when he recited: "To Allah belongs whatever is in the heavens and whatever is on the earth. And whether you show what is in your hearts or conceal it, Allah will call you to account for it" [Surah al-Baqarah: 284]. Ibn Umar (may Allah be pleased with them both) began to sob, so much so that Ibn Abbas (may Allah be pleased with them both) heard his sobbing at the back of the mosque. Ibn Umar (may Allah be pleased with them both) said: We will be taken to account even for the whisperings of our hearts. Sa'id bin Marjanah said: So I asked Ibn Abbas (may Allah be pleased with them both) about what I had witnessed and told him about it. He said: May Allah forgive Abu Abd al-Rahman. The Muslims too felt the same distress from this verse that he felt, and they complained about it to the Messenger of Allah (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) said: "This is what your Lord has said, so say: We believe in what has been revealed; we hear and we obey; (we seek) Your forgiveness, our Lord, and to You is the return." So they kept saying it for as long as Allah willed that they should say it, until Allah, the Mighty and Majestic, revealed: "The Messenger believes in what has been revealed to him from his Lord" [Surah al-Baqarah: 285] up to: "Allah does not burden any soul beyond its capacity" [Surah al-Baqarah: 286].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10724