Thus, with the common denominator the shares are: — husband = 3/6 and two sisters = 4/6. (The sum of the numerators is 7.] Now, the common denominator is increased to the sum of the numerators, (i.e., 7). On doing this, the shares would be as follows: husband: 3/7 and two sisters 4/7 (3/7 + 4/7 = 1.)
It may be noted that this doctrine is called “increase”, not because the shares are increased, which is quite the opposite, the very object of the doctrine being to diminish the shares, but because the unity is reached by increasing the denominator of the fractional shares.
In other words, if it is found, on assigning their respective shares to the sharers, that the sum total of the shares exceeds unity, the share of each sharer is proportionately diminished, by reducing the fractional shares to a common denominator and increasing the denominator, so as to make it equal to the sum of the numerator.
Difference between Shia and Sunni Law of ‘Increase’:
According to the Sunni law, the doctrine implies proportionate reduction of all the shares. According to the Shia law, on the other hand, it implies the reduction of the shares of the daughter or the daughter and full or consanguine sister or sisters only. Other heirs do not suffer.
The following are a few illustrative examples of the application of the Doctrine of Increase:
(a) Husband 1/2 = 3/6 reduced to 3/8
2 Full sisters 2/3 = 4/6 reduced to 4/8
Mother 1/6 = 1/6 reduced to 1/8
Total: 8/6 8/8
(b) Husband 1/4 = 3/12 reduced to 3/13
Mother 1/6 = 2/12 reduced to 2/13
2 Daughters 2/3 = 8/12 reduced to 8/13
Total: 13/12 13/13
(c) Widow 1/4 = 3/12 reduced to 3/13
Mother 1/3 = 4/12 reduced to 4/13
Full sister 1/2 = 6/12 reduced to 6/13
Total: 13/12 13/13
(d) Husband 1/4 = 3/12 reduced to 3/15
Father 1/6 = 2/12 reduced to 2/15
Mother 1/6 = 2/12 reduced to 2/15
3 Daughters … 2/3 = 8/12 reduced to 8/15
Total: 15/12 15/15