When you cannot decide
The Prophet ﷺ taught this for every matter, as he taught sūrahs of the Qur'an.
ُ اللَّهُمَّ إِنِّي أَسْتَخِيرُكَ بِعِلْمِكَ، وَأَسْتَقْدِرُكَ بِقُدْرَتِكَ، وَأَسْأَلُكَ مِنْ فَضْلِكَ الْعَظِيمِ، فَإِنَّكَ تَقْدِرُ وَلاَ أَقْدِرُ، وَتَعْلَمُ وَلاَ أَعْلَمُ، وَأَنْتَ عَلاَّمُ الْغُيُوبِ، اللَّهُمَّ إِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الأَمْرَ خَيْرٌ لِي فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي ـ أَوْ قَالَ عَاجِلِ أَمْرِي وَآجِلِهِ ـ فَاقْدُرْهُ لِي، وَإِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الأَمْرَ شَرٌّ لِي فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي ـ أَوْ قَالَ فِي عَاجِلِ أَمْرِي وَآجِلِهِ ـ فَاصْرِفْهُ عَنِّي وَاصْرِفْنِي عَنْهُ، وَاقْدُرْ لِيَ الْخَيْرَ حَيْثُ كَانَ، ثُمَّ رَضِّنِي بِهِ. وَيُسَمِّي حَاجَتَهُ
Allāhumma innī astakhīruka bi-ʿilmik, wa astaqdiruka bi-qudratik, wa as'aluka min faḍlika-l-ʿaẓīm…
“O Allah, I seek Your guidance by Your knowledge, and Your power by Your might, and I ask You of Your immense grace… (prayed after two rakʿahs, naming your need)”
The full narration
Narrated Jabir:The Prophet (ﷺ) used to teach us the Istikhara for each and every matter as he used to teach us the Suras from the Holy Qur'an. (He used to say), "If anyone of you intends to do something, he should offer a two-rak`at prayer other than the obligatory prayer, and then say: 'Allahumma inni astakhiruka bi'ilmika, wa astaqdiruka biqudratika, wa as'aluka min fadlika-l-'azim, fa innaka taqdiru wala aqdiru, wa ta'lamu wala a'lamu, wa anta'allamu-l-ghuyub. Allahumma in kunta ta'lamu anna hadha-lamra khairun li fi dini wa ma'ashi wa 'aqibati `Amri (or said, fi 'ajili `Amri wa ajilihi) fa-qdurhu li, Wa in kunta ta'lamu anna ha-dha-l-amra sharrun li fi dini wa ma'ashi wa 'aqibati `Amri (or said, fi ajili `Amri wa ajilihi) fasrifhu 'anni was-rifni 'anhu wa aqdur li alkhaira haithu kana, thumma Raddani bihi," Then he should mention his matter (need)
Source
Ṣaḥīḥ al-Bukhārī · 6382
- Agreed upon as authentic (al-Bukhārī / Muslim)