Article 282 of CoI : Article 282: Expenditure defrayable by the Union or a State out of its revenues.

Explanation using Example

Example 1:

The central government (Union) decides to allocate funds to a state government for the construction of a new hospital in a rural area. Although healthcare is primarily a state subject, the Union government can still make this grant to the state for the public purpose of improving healthcare facilities.

Example 2:

A state government wants to promote tourism in a particular region by organizing a cultural festival. Although tourism promotion is not explicitly listed as a subject on which the state legislature can make laws, the state government can still use its revenues to fund the festival because it serves the public purpose of boosting local economy and culture.