When total training volume is equated, resistance training with repetitions stopped short of muscular failure produces the same degree of muscle hypertrophy as resistance training performed to muscular failure.

Study: Strength Training with Repetitions to Failure does not Provide Additional Strength and Muscle Hypertrophy Gains in Young Women

When people lift the same total amount of weight, it doesn't matter if they push until they can't move anymore or stop just before — they grow muscle just as much. The study showed both groups grew muscle similarly, as long as they lifted the same total weight.

Study: Effect of resistance training to muscle failure vs non-failure on strength, hypertrophy and muscle architecture in trained individuals

When people lifted weights until just before exhaustion versus until complete exhaustion, both groups ended up with nearly the same muscle growth, even though one group did fewer reps. So, you don’t need to push to absolute failure to build muscle if you’re doing enough work.

Study: Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training

When lifting heavy weights, it doesn't matter if you go all the way to failure or stop just before — you still grow about the same amount of muscle, as long as you lift the same total weight. But with light weights, you need to go closer to failure to see muscle growth.

Study: Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals

When people lift weights with the same total effort, it doesn't matter if they stop just before exhaustion or push until they can't do another rep—both ways build about the same amount of muscle.