Some scholars described the hadith "Actions are judged by intentions" as half of the religion, because Islam is built upon both outward and inward deeds. This hadith explains the foundation of inward deeds—namely intention (niyyah) and sincerity (ikhlās)—while other texts address outward deeds and adherence to the Sunnah.
The religion that Allah has prescribed consists of two fundamental aspects:
For this reason, some scholars explained that the religion consists of an inward and an outward dimension, and that the hadith "Actions are judged by intentions" addresses the foundation of the inward deeds.
The scholars unanimously agreed that a deed is accepted by Allah only when two conditions are fulfilled:
This relates to intention and the actions of the heart, which is the meaning of the Prophet's ﷺ statement:
"Actions are judged by intentions, and every person will have only what he intended."
This relates to the correctness of the deed and its conformity with the Sunnah, as indicated by the hadith:
"Whoever introduces into this matter of ours that which is not part of it, it will be rejected."
Therefore, the scholars said that the hadith of intentions is the criterion for inward deeds, while the hadith "Whoever introduces..." is the criterion for outward deeds.
Because the religion combines two essential elements:
The hadith of intentions explains the aspect of sincerity and intention, making it half of the religion from this perspective, while the hadith "Whoever introduces into this matter of ours that which is not part of it, it will be rejected" explains the aspect of following the Sunnah and outward actions.
Shaykh al-Islam Ibn Taymiyyah, Ibn Rajab, and other scholars stated that the hadith "Actions are judged by intentions" is the standard for inward deeds, just as the hadith "Whoever introduces into this matter of ours that which is not part of it, it will be rejected" is the standard for outward deeds.
Shaykh Ibn Baz رحمه الله also said:
"Some scholars said that it represents half of the religion because the religion consists of two halves: one related to the heart and the other related to outward actions. This hadith concerns the heart."
And Allah knows best.