Musnad Ishaq

Benefits:
From the mentioned hadith, the virtue of standing (in prayer) during Laylat al-Qadr is established. It is also understood that faith (iman) is a condition for the acceptance of deeds. If someone performs actions without faith—even if it is service to creation, maintaining family ties, constructing the House of Allah, or serving the pilgrims—these will not be accepted by Allah; rather, they will be entirely weightless in the sight of Allah. As Allah the Exalted says:
﴿وَالَّذِیْنَ كَفَرُوْا اَعْمَالُهُمْ كَسَرَابٍ بِّقِیعَةٍ یَحْسَبُهُ الظَّمْآنُ مَاءً حَتّٰی اِذَا جَاء لَمْ یَجِدْهُ شَیْئًا وَّوَجَدَ اللّٰهَ عِنْدَہٗ فَوَفَّاهُ حِسَابَهٗ﴾ (an-Nur: 39) .... “And the deeds of those who disbelieve are like a mirage in a desert, which the thirsty one thinks is water, until when he comes to it, he finds it is nothing, but finds Allah with him, who will pay him his due in full.” Further explanation can be seen in the tafsir of Surah al-Qadr.

By the forgiveness of past sins, minor sins (saghirah) are meant, not major sins (kabirah). However, sometimes due to a particular good deed, Allah, the Possessor of Majesty, also forgives major sins.