After the cacophony of screeching brakes and grinding gears, there followed the comparatively static hum of engines, and drivers waited in exasperation for the next lurch forwards. For the moment there was a lull, curious on that highway. Then the waiting very quickly began to fray at the edges. The sun was beating on the metal of the vehicles, and the road lay flattened across the parched plain, with no trees to screen it from the sun. First one car horn began to honk, then a bicycle rickshaw began to clang its bell, then a truck blared its musical horn, and then the lesser ones began to go pom-pom, pom-pom almost in harmony, and suddenly, out of the centre of all that noise, a long, piercing wail emerged.

Inside him, he felt a boundless power, an imperishable energy, an ability to achieve anything with confidence, precision, and obvious success. His heart was overflowing with love for people, animals, and things and with an all-engulfing sense of optimism and joy. It was as if he were no longer troubled or bothered by fear, anxiety, sickness, death, argument, or the question of earning a living. Even more important than that, and something he could not analyze, it was a feeling which penetrated to every cell of his body and soul; it played a tune full of delight, pleasure, serenity, and peace and hummed in its incredible melodies the whispering sound of the world which is denied to the unhappy.
Which is the best example of personification:
every cell of his body and soul
a boundless power
an ability to achieve anything with confidence
the whispering sound of the world

the whispering sound of the world

The best example of personification in the given passage is "the whispering sound of the world." Personification is when human characteristics are given to non-human entities. In this case, the sound of the world is being described as "whispering," which is a human characteristic (humans can whisper).