Indivisible obligation

Article 1223 of the Civil Code refers to divisibility or indivisibility of prestation, to wit:
ART. 1223. The divisibility or indivisibility of the things that are the object of obligations in which there is only one debtor and only one creditor does not alter or modify the provisions of Chapter 2 of this Title. (1149)
In indivisible obligation, the object is not capable of partial performance. For example, A agreed to sing B a birthday song for Php50.00. The object in their contract is not capable of partial performance. Hence, it is an indivisible obligation.

Moreover, there are three kinds of indivisibility:[1] a) legal indivisibility, where a specific provision of law declares an obligation which is divisible in nature an indivisible one; b) conventional indivisibility, where the obligation is divisible but the will of the parties makes it indivisible; and c) natural indivisibility, where an obligation is indivisible because of its nature.

[1] De Leon. (2014). Obligations and Contracts.