Narrated ‘Ali (radiallaahu `anhu):
Allah’s Apostle (sallallaahu `alayhi wasallam) ordered me to give in charity the skin and the coverings of the Budn which I had slaughtered.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
If we say concerning the hadiy and udhiyah that it is mustahabb to eat one third and give one third in charity, that only applies if there is no reason to increase the portion of one of the categories of recipients. But if it so happens that there are a lot of poor people, then we regard it as preferable to give more than one third in charity; the same applies if the poor have received meat in abundance (in this case, their share may be reduced); and the same applies to what one may keep. Wherever the need is greatest, that may change the ratios given to the three categories of recipients.
Majmoo‘ al-Fataawa, 19/258