In the Musnad, there is a Hadith from Al-Bara' bin `Azib that a man asked, "O Allah's Messenger! Direct me to an action that draws me closer to Paradise and away from the Fire.'' The Messenger of Allah said,

«أَعْتِقِ النَّسَمَةَ وَفُكَّ الرَّقَبَة»

(Emancipate the person and free the neck (slave).) The man asked, "O Allah's Messenger! Are they not one and the same'' He said,

«لَا، عِتْقُ النَّسَمَةِ أَنْ تُفْرِدَ بِعِتْقِهَا، وَفَكُّ الرَّقَبَةِ أَنْ تُعِينَ فِي ثَمَنِهَا»

(No, you emancipate a person by freeing him on your own, but you untie a neck (slave) by helping in its price.)