«فَاسْتَعَدْتُهُ وَقُلْتُ لَهُ: قَدْ عَرَفْتُ بُوشِيكَ، فَاسْتَقِمْ فِي مَشِيكَ»
I called him back and said that I recognised his polished speech; now he should also walk straight.
Būshīk points to his polished and ornamented speech, while mashīk is his manner of walking. The sounds work together in a teasing admonition.
The line balances recognition with playful reproach. Al-Ḥārith is inviting the stranger to give up the pretence rather than simply asking his name.