"Intercede, you will be rewarded." اشفعوا تؤجروا
This authentic, two-word Hadith narrated by Abu Dawud, Nasai, and Bukhari, is supported by what Allah said in the Qur'an: "Whoever intercedes for a good cause will have a reward therefrom; and whoever intercedes for an evil cause will have a burden therefrom. And ever is Allah , over all things, a Keeper" [4:85].
In the hereafter, Allah will allow the intercession of the prophet, the martyrs, the hafiz (memorizers of Qur'an), parents for their righteous children and vice versa, children that died before the age of puberty, forty Muslims attending a funeral for the deceased.
In this life we have two types of intercessions: the allowed and the prohibited. Examples of the allowed intercession include helping out a brother or sister in debt, sponsoring a refugee, praying for others in their absence, etc. Any intercession that takes or violates the right of others is prohibited. Examples of such intercessions include helping someone obtain prohibited things like alcohol, helping a criminal to illegally escape punishment stipulated by the law because of his wealth or social status, although settling a case before bringing it to the authorities is acceptable.
Intercession becomes mandatory in some cases, such as interceding to save someone's life, or to protect the honor of an innocent person.
The Hadith about the prophet refusing to meet with an inquirer until his companions intercede so that the companions could get rewarded for interceding teaches us an important lesson on the virtue of interceding and helping others get rewards.