The means and actions by way of which reward (for deeds) are increased—Imaam Sadi (rahimahullaah)
بِسۡمِ ٱللهِ ٱلرَّحۡمَـٰنِ ٱلرَّحِيمِ
And from the means of increasing the (reward for good deeds) is the basis and foundation of what has preceded [see here:wp.me/p4cUPQ-8a] and that is (the presence of) sound Aqeedah; a strong belief in Allaah and in His Attributes; a slave’s strong desire (to worship Allaah –fulfilling the commandments and keeping away from the forbidden affairs with perfection) and his fervent desire for goodness. For indeed those who are the genuine Ahlus Sunnah Wal-Jamaa-ah and those people of knowledge (i.e. the Rabbaani scholars)who possess knowledge of the perfect and detailed (explanation) of the Names and Attributes of Allaah and have a strong desire for the meeting with Him (in the Afterlife); the reward for their deeds are greatly increased in a manner in which others who share the same belief can neither reach nor approach in the least. And this is why the Salaf used to say: When Ahlus Sunnah are held back by their deeds (i.e. not having numerous deeds), they are supported by their soundcreed (through which the reward for their good deeds accompanied by strong Imaan, sound Aqeedah and adherence to the authentic Sunnah are increased). And based on this, then Ahlus Sunnah are the guided ones and ahlul bidah are the misguided ones. It is well known that there is a difference between the one who traverses the straight path and the one who is deviated from it towards the path of the hellfire, and the end result of this (misguided) person is either that he is excused for his misguidance or he may not be excused.
[Source: See Fatawaa As-Sadiyyah page: 44 and Sharh Al-Asbaab Wal-A’maal Allatee Yudaa-afu Bihaa Ath-Thawaabpage: 59-65. Slightly paraphrased]