For Marriage
It is very bad; they will mislead you. Do not perform it under any circumstances.
For Business / Deal
They are deceiving you and will inflict a massive financial loss upon you.
الَّذِينَ يَتَرَبَّصُونَ بِكُمْ فَإِن كَانَ لَكُمْ فَتْحٌ مِّنَ اللَّهِ قَالُوا أَلَمْ نَكُن مَّعَكُمْ وَإِن كَانَ لِلْكَافِرِينَ نَصِيبٌ قَالُوا أَلَمْ نَسْتَحْوِذْ عَلَيْكُمْ وَنَمْنَعْكُم مِّنَ الْمُؤْمِنِينَ ۚ فَاللَّهُ يَحْكُمُ بَيْنَكُمْ يَوْمَ الْقِيَامَةِ ۗ وَلَن يَجْعَلَ اللَّهُ لِلْكَافِرِينَ عَلَى الْمُؤْمِنِينَ سَبِيلًا
Allatheena yatarabbasoona bikum fain kana lakum fathun mina Allahi qaloo alam nakun maAAakum wain kana lilkafireena naseebun qaloo alam nastahwith AAalaykum wanamnaAAkum mina almumineena faAllahu yahkumu baynakum yawma alqiyamati walan yajAAala Allahu lilkafireena AAala almumineena sabeelan
(These are) the ones who wait and watch about you: if ye do gain a victory from Allah, they say: "Were we not with you?"- but if the unbelievers gain a success, they say (to them): "Did we not gain an advantage over you, and did we not guard you from the believers?" but Allah will judge betwixt you on the Day of Judgment. And never will Allah grant to the unbelievers a way (to triumphs) over the believers.