Tirmidhi

Explanation:
1:
When they commit any indecent act or fall into any sin, they immediately remember Allah and seek forgiveness for their sins (Aal Imran: 135).

Fiqh al-Hadith:
Man is prone to error; forgetfulness is part of his nature and innate disposition. However, it is the way of the believer that, upon making a mistake, he feels remorse and turns back to his Lord. The habit of the disbeliever and the wrongdoer is that they persist in their sins. It is from the grace and kindness of Allah, the Exalted, that He calls His sinful servants towards forgiveness and pardon. Whoever presents himself at His door finds Him not only Forgiving (Ghafur) but also Merciful (Rahim). It was the practice of our predecessors that whenever they erred, they would immediately turn back to Allah.

❀ Sayyiduna Siddiq Akbar radi Allahu anhu heard the Messenger of Allah sallallahu alayhi wa sallam saying:
«ما من عبد يذنب ذنبا فيحسن الطهور ثم يقوم فيصلي ركعتين، ثم يستغفر الله إلا غفر له، ثم قرأ هٰذه الآية : ”والذين إذا فعلوا فاحشة أو ظلموا أنفسهم ذكروا الله فاستغفروا لذنوبهم“» [آل عمران : 135 الآية .]
“When a servant commits a sin, then performs ablution (wudu) well and stands to pray two units (rak‘ah), and then asks Allah for forgiveness, Allah forgives him.” He sallallahu alayhi wa sallam then recited this verse: “Those who, when they commit an evil deed or wrong themselves, remember Allah and seek forgiveness for their sins.” [مسند الإمام أحمد : 10/1، سنن أبى داو، د : 1521، سنن الترمذي : 604، 3006، السنن الكبريٰ للنسائي : 11078، عمل اليوم والليلة للنسائي : 417، سنن ابن ماجة : 1395، شعب الايمان للبيهقي : 7079، وسنده، حسن]

This hadith was:
◈ Declared “Sahih” by Imam Ibn Hibban rahimahullah (623).
◈ Declared “Hasan” by Imam Tirmidhi rahimahullah.
◈ Imam Ibn ‘Adi rahimahullah said:
«وهٰذا الحديث طريقه، حسن وأرجو أن يكون صحيحا .»
“The chain of this hadith is hasan, and it is hoped that it is sahih.” [الكامل فى ضعفاء الرجال : 431/1]
◈ Hafiz Ibn Hajar rahimahullah said: This hadith is “jayyid al-isnad (of strong chain).” [تهذيب التهذيب : 235/1]
◈ Hafiz ‘Alai rahimahullah said: «حديث ثابت» “This hadith is established.” [جامع التحصيل فى أحكام المراسيل، ص : 57]
◈ Hafiz Dhahabi rahimahullah said: «اسناده، حسن» “Its chain is hasan.” [تذکرۃ الحفاظ : 11/1]
◈ Hafiz Ibn Kathir rahimahullah [تفسیر ابن کثیر : 1/407] declared it “hasan.”
↰ According to the majority, Asma’ bin Hakam is «حسن الحديث».

1521. Commentary:
➊ When Ali radi Allahu anhu would require an oath from other noble Companions radi Allahu anhum regarding narrations of hadith, it was for the sake of increased reliability. And acting upon the statement of the Prophet sallallahu alayhi wa sallam only becomes obligatory when it is authentically established with all its complete conditions.
➋ Despite such diligence, he did not dare to require an oath from Abu Bakr as-Siddiq radi Allahu anhu. In this is a clear proof of the lofty status of as-Siddiq radi Allahu anhu, his respect, deep trust in his truthfulness, and the splendid evidence of their mutual brotherly relations.
➌ Performing prayer (salah) with the intention of repentance and seeking forgiveness is recommended (mustahabb).

Benefits and Issues:

➊
The practice of caution in accepting the Prophetic hadith (sallallahu alayhi wa sallam) and distinguishing between the authentic and the weak began with the noble Companions (radi Allahu anhum ajma'in).

➋
The reason why Ali (radi Allahu ta'ala anhu) would not take an oath was not because he lacked trust in the narrations of the Companions (radi Allahu anhum ajma'in).
Rather, the purpose was that others would realize the importance of hadith,
and only narrate those hadith which they remembered well.
In addition, another benefit intended was
that if they narrated a hadith to someone, they would do so with full confidence that the hadith is authentic.

➌
Ali (radi Allahu ta'ala anhu) had such certainty in the truthfulness of Abu Bakr as-Siddiq (radi Allahu ta'ala anhu) that he would accept any hadith narrated by him without hesitation.

➍
Ablution (wudu) and prayer (salah) are means for the forgiveness of sins.

➎
Despite performing prayer, it is necessary to supplicate to Allah for forgiveness with a remorseful heart.
However, some minor sins are forgiven by ablution alone or by prayer alone.

Benefit:
In this hadith, it is also stated that utmost caution is required in receiving a hadith or conveying it further. This caution, especially in receiving hadith, began with the noble Companions (radi Allahu anhum ajma'in) themselves. Now, the people of knowledge have abandoned this caution, and have neglected attention towards hadith and the sciences of hadith.

It is also established from this hadith that sins are forgiven through ablution (wudu), prayer (salah), and seeking forgiveness (istighfar).