humility / modesty
Form VI maṣdar (تَفَاعُل). Verb: تَوَاضَعَ (to humble oneself). هَوْنًا in the verse means gently/humbly. Opposite of كِبْر (arrogance).
The 'servants of ar-Raḥmān' passage (25:63-77) describes the ideal Muslim character - beginning with humility in daily conduct.