Shafa’ah literally denotes the pairing of two things and is commonly used for when a respected person intercedes with a high rank and the like for one who has committed a crime of some sort, asking for his forgiveness, or for him to increase the reward for a good thing the person being interceded for has done. Maybe the reason this word has been used for such an act is because the criminal himself in no way deserves to be forgiven, and that is why he has to be paired with the request and intercession of the respected person in order to be forgiven.
According to Islamic teachings, shafa’ah means intercession with Allah (swt) for something good to be granted to someone, or for a bad thing to be prevented from reaching him/her. What must be noted is that this is something that Allah (swt) himself has formulated for those who hardly deserve any grace and mercy from Him, and it is He who defines the borders and rules for it. What Shafa’ah actually refers to in Islamic terms, is for a sinner, who can't present his deeds [because he hardly has any good deeds] to Allah (swt) in order to be delivered from a state that entails punishment and chastisement, to have a relationship with an intercessor so that he will be freed of such a state and forgiven as a result.
So, according to Islam, shafa’ah isn't an unconditional subject without any boundaries, but has conditions and criteria that have to do with the type of sin committed and who the intercessor and the one being interceded for are. Unless the conditions are met, there will be no shafa’ah.
Belief in such a concept has a significant impact on sinners and them making an effort to discontinue their ways and strive for acquiring virtue and perfection.
Shafa’ah (شفاعة) derives from the root word shaf’ (شفع) which means to pair with or to attach something to another similar thing, and has been later used for the combining of a stronger individual with a weaker one in order to help him.
This term is commonly used to denote when a person makes use of his respected status to change the mind of one bearing power and authority regarding the punishment of someone. This usually takes place because of the sway the intercessor has or the fear others have of him, and sometimes because of him using certain methods and tactics to change the mind of the authority about the one to be punished, arousing his feelings, etc. In all of such cases, there is no change in the behavior and mindset of the criminal, the only person who experiences any substantial change is the one being interceded with.
This type of intercession absolutely doesn’t exist in the Quran and Islamic teachings, because neither does Allah (swt) ever mistake in order for there to be any need of someone else showing him the right way so that he changes His mind, nor does he have feelings and emotions like us that can be aroused, nor is He afraid of others; He always observes justice in His judgments, so there are no misjudgments and injustices that need to be corrected through intercession.
The intercession the Quran and Islamic teachings speak of, is one that circles around the changing of the one being interceded for. What takes place in this type of intercession, is that the one being interceded for does some things that help him leave the state of deserving punishment and enter a new state in which makes him deserve forgiveness as a result of having a relationship with the intercessor. Believing in such an intercession has a great impact on the training and correction of sinners, because if those who have committed great sins and at the same time regret it feel that there is no way back and that they there is no way to be freed of otherworldly punishment, they might become worse and commit even greater sins and crimes as a result of their hopelessness. They might say that what they have done is society’s fault, causing them to take revenge of society. But one who believes in intercession and that there is always a small window open to forgiveness and hope will consider changing, practicing self-restraint and returning to the right path and even making up for the past; this will result in both the person becoming better and society being more secure and peaceful.
At the same time, shafa’ah and intercession in Islam isn't something without any conditions; there are criteria that apply to the sin and crime one has committed, who the one being interceded for is and who the intercessor is. Those who believe in intercession and look to be able to take advantage of this precious opportunity in the future need to meet the necessary criteria and refrain from sins like oppression, shirk, etc. They also need to be in a way that those to intercede on the Day of Judgment will pay attention to them and intercede for them and so on.
All of these are proof that the intercession the Quran speaks of is a precious thing that results in the spiritual development of those in society, the main goal of all prophets.
In other words, in common everyday usage, intercession means for a respected person to ask a high ranked individual to overlook a punishment or to give more incentives to someone. In these cases, one who accepts another’s intercession might have his own reasons; reasons and needs that have no way in Allah (swt).
Allah (swt) doesn’t accept the intercession of those He has permitted out of fear or need; it is merely a way He himself has determined for those who are the least deserving of His forgiveness, limiting it to certain conditions.
Of course, the term shafa’ah has also been used in Islamic terms for a vaster meaning that covers all positive effects. For instance, when it is said that the parents will do shafa’ah for their children and vice versa, or that teachers will do shafa’ah for their students, or that the mo’adhins (callers to prayer and reciters of the adhan) will do shafa’ah for those who have remembered the prayer and have gone to the masjid as a result of their adhans, what is meant is that their acts will have the same positive effects they had in this world, in the hereafter, and will help them.
It is on this basis that asking for the forgiveness of the sinners and praying for others in this world is considered a form of shafa’ah and intercession with Allah (swt), because all of them are considered mediation for good to be channeled to others, or for bad to be kept away from them.