The Messenger of Allah ﷺ used to observe four rak'ahs in the forenoon prayer and he sometimes observed more as Allah pleased. (Using translation from Muslim 719c)
كَانَ رَسُولُ اللهِ ﷺ «يُصَلِّي الضُّحَى أَرْبَعًا وَيَزِيدُ مَا شَاءَ اللهُ» خَالَفَهَا عُرْوَةُ