Union Government
(1) Subject to any law made by Parliament, the Supreme Court may, with the President's approval, make rules regulating its own practice and procedure, including rules on who can practise before it, appeal procedures, Fundamental Rights enforcement proceedings, review procedures, costs, bail, stay of proceedings, and summary dismissal of frivolous appeals. (2)-(3) These rules can fix the minimum number of Judges for various purposes; deciding a substantial constitutional-interpretation question, or a Presidential Reference under Article 143, requires a minimum bench of five Judges. (4)-(5) Judgments and opinions must be delivered in open Court, with the concurrence of a majority of Judges present, though a dissenting Judge may still deliver a separate dissenting judgment or opinion.
The Supreme Court largely sets its own detailed procedural rules for how it functions - but importantly, any case genuinely involving a significant constitutional-interpretation question must be decided by a bench of at least five judges (a "Constitution Bench"), not a smaller panel, reflecting the special weight given to constitutional questions.
This is why major constitutional cases - like those involving the scope of Fundamental Rights or the basic structure doctrine - are typically decided by a Constitution Bench of five or more judges, rather than the smaller two- or three-judge benches that hear most routine appeals.