From Wiktionary, the free dictionary
Adverbial accusative of بَاطِل (bāṭil, “vain”).
بَاطِلًا • (bāṭilan)
- for no purpose, uselessly, for nothing, futilely
609–632 CE, Qur'an, 3:191:رَبَّنَا مَا خَلَقْتَ هَـٰذَا بَـٰطِلًۭا- Our Lord! You have not created ˹all of˺ this without purpose.