Sacrifice - rules, guidelines and modern issues

 Reward in lieu of every hair of the animal

There is a Hadith in Sunan Ibn Majah about the reward of sacrificing an animal:

Hadhrat Zaid bin Arqam (May Allah be well pleased with him) narrates, a companion of the Holy Prophet (Sallallahu alaihi wa sallam) asked Him:  O Prophet of Allah (Sallallahu alaihi wa sallam)!  What is sacrifice?  The Holy Prophet (Sallallahu alaihi wa sallam) replied:  It is the practice of your father Ibrahim (May peace be upon him).  Then he asked: What is there for us in it O Prophet of Allah (Sallallahu alaihi wa sallam)?  The Holy Prophet replied: There is a reward for every hair.  Again he asked:  O Prophet of Allah (Sallallahu alaihi wa sallam)! Then what is the wool for? The Holy Prophet (Sallallahu alaihi wa sallam) replied: There is a reward for every little strand of wool.

(Sunan Ibn Majah, Hadith No. 3247)

On the day of Eid Ul Azha, there is no money better than the one which is spent for sacrificing an animal, as mentioned in this Hadith of Shu‘abul Iman:

It is narrated on the authority of Hadhrat ‘Abdullah Bin Abbas (May Allah be well pleased with them) that the Holy Prophet (Sallallahu alaihi wa sallam) said: On the day of Eid, the best Dirham is the one spent on the animal being slaughtered.

(Shu‘abul Iman, Hadith No. 7084)