For Marriage
They are hiding an important matter from you. This marriage is not advisable (Salah). Wait and put your Tawakkul in Allah.
For Business / Deal
They are hiding a matter from you. Withdraw from this deal and put your Tawakkul in Allah.
الَّذِينَ آتَيْنَاهُمُ الْكِتَابَ يَعْرِفُونَهُ كَمَا يَعْرِفُونَ أَبْنَاءَهُمْ ۖ وَإِنَّ فَرِيقًا مِّنْهُمْ لَيَكْتُمُونَ الْحَقَّ وَهُمْ يَعْلَمُونَ
Allatheena ataynahumu alkitaba yaAArifoonahu kama yaAArifoona abnaahum wainna fareeqan minhum layaktumoona alhaqqa wahum yaAAlamoona
The people of the Book know this as they know their own sons; but some of them conceal the truth which they themselves know.