إِن تُصِبْكَ حَسَنَةٌ تَسُؤْهُمْ وَإِن تُصِبْكَ مُصِيبَةٌ يَقُولُوا۟ قَدْ أَخَذْنَآ أَمْرَنَا مِن قَبْلُ
In tuṣibka ḥasanatun tasuʾhum; wa in tuṣibka muṣībatun yaqūlū qad akhadhnā amranā min qablu wa yatawallaw wa hum fariḥūn · Qul lan yuṣībanā illā mā kataba'llāhu lanā; huwa mawlānā; wa ʿala'llāhi fa'l-yatawakkali'l-muʾminūn · Qul hal tarabbaṣūna binā illā iḥda'l-ḥusnayayni; wa naḥnu natarabbaṣu bikum an yuṣībakumu'llāhu bi-ʿadhābin min ʿindihī aw bi-aydīnā; fa-tarabbaṣū innā maʿakum mutarabbiṣūn
"If good comes to you it grieves them; and if a misfortune befalls you they say, 'We took our precautions beforehand,' and they turn away rejoicing. · Say: nothing will befall us but what God has written for us. He is our protector; and in God let the believers put their trust. · Say: are you waiting for anything to happen to us but one of the two good things? We too are waiting for God to bring you a punishment from Himself or by our hands. Wait, then; we are waiting with you."
The verse names both of the two possibilities as good. In the classical commentaries it is widely reported that these two are victory and martyrdom.
I record this as my own reading, and its ground is the dual al-ḥusnayayn: the sentence does not accept the gain/loss pairing set up by the ones addressed. The other side is waiting for two outcomes; the verse names both of those outcomes with a single word.
The sense of the root: to wait and watch for a thing to happen. And the same root occurred as a command in verse 24 of the sūra: fa-tarabbaṣū ḥattā yaʾtiya'llāhu bi-amrih.
I record this as an observation: the same verb is given to both sides — waiting is what both sides do. The difference lies in what is waited for.