Masruq (may Allah have mercy on him) said: I asked Ibn Mas'ud (may Allah be pleased with him) about al-suht (unlawful gain), and he said: "It is bribery." And I asked about injustice in judgement, and he said: "That is disbelief."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20479