وَلَا تَأْكُلُوٓا۟ أَمْوَٰلَكُم بَيْنَكُم بِٱلْبَٰطِلِ وَتُدْلُوا۟ بِهَآ إِلَى ٱلْحُكَّامِ لِتَأْكُلُوا۟ فَرِيقًۭا مِّنْ أَمْوَٰلِ ٱلنَّاسِ بِٱلْإِثْمِ وَأَنتُمْ تَعْلَمُونَ ﴿١٨٨﴾
你们不要借诈术而侵蚀别人的财产，不要以别人的财产贿赂官吏，以便你们明知故犯地借罪行而侵蚀别人的一部分财产。
Doubtful: be careful Money & business
Can I accept a gift or a meal from someone whose income is mixed?
Short answer
This is doubtful. If most of a person's income is lawful, scholars generally allow accepting a gift or meal from them. If you know the item itself came from a haram source, do not take it. If you are unsure, it is better to leave the doubtful, as the Prophet ﷺ taught.
Evidence
Quran
Hadith
Sahih al-Bukhari 52
Narrated An-Nu'man bin Bashir: I heard Allah's Messenger (ﷺ) saying, 'Both legal and illegal things are evident but in between them there are doubtful (suspicious) things and most of the people have no knowledge about them. So whoever saves himself from these suspicious things saves his religion and his honor. And whoever indulges in these suspicious things is like a shepherd who grazes (his animals) near the Hima (private pasture) of someone else and at any moment he is liable to get in it. (O people!) Beware! Every king has a Hima and the Hima of Allah on the earth is His illegal (forbidden) things. Beware! There is a piece of flesh in the body if it becomes good (reformed) the whole body becomes good but if it gets spoilt the whole body gets spoilt and that is the heart
Arabic text (with chain of narrators)
حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا زَكَرِيَّاءُ، عَنْ عَامِرٍ، قَالَ سَمِعْتُ النُّعْمَانَ بْنَ بَشِيرٍ، يَقُولُ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " الْحَلاَلُ بَيِّنٌ وَالْحَرَامُ بَيِّنٌ، وَبَيْنَهُمَا مُشَبَّهَاتٌ لاَ يَعْلَمُهَا كَثِيرٌ مِنَ النَّاسِ، فَمَنِ اتَّقَى الْمُشَبَّهَاتِ اسْتَبْرَأَ لِدِيِنِهِ وَعِرْضِهِ، وَمَنْ وَقَعَ فِي الشُّبُهَاتِ كَرَاعٍ يَرْعَى حَوْلَ الْحِمَى، يُوشِكُ أَنْ يُوَاقِعَهُ. أَلاَ وَإِنَّ لِكُلِّ مَلِكٍ حِمًى، أَلاَ إِنَّ حِمَى اللَّهِ فِي أَرْضِهِ مَحَارِمُهُ، أَلاَ وَإِنَّ فِي الْجَسَدِ مُضْغَةً إِذَا صَلَحَتْ صَلَحَ الْجَسَدُ كُلُّهُ، وَإِذَا فَسَدَتْ فَسَدَ الْجَسَدُ كُلُّهُ. أَلاَ وَهِيَ الْقَلْبُ ".
This is general information, not a fatwa. For your own situation, ask a qualified scholar.
Questions about halal and haram
Can I accept a gift or a meal from someone whose income is mixed?
This is doubtful. If most of a person's income is lawful, scholars generally allow accepting a gift or meal from them. If you know the item itself came from a haram source, do not take it. If you are unsure, it is better to leave the doubtful, as the Prophet ﷺ taught.