The Quran

سَيَقولُ المُخَلَّفونَ إِذَا انطَلَقتُم إِلىٰ مَغانِمَ لِتَأخُذوها ذَرونا نَتَّبِعكُم ۖ يُريدونَ أَن يُبَدِّلوا كَلامَ اللَّهِ ۚ قُل لَن تَتَّبِعونا كَذٰلِكُم قالَ اللَّهُ مِن قَبلُ ۖ فَسَيَقولونَ بَل تَحسُدونَنا ۚ بَل كانوا لا يَفقَهونَ إِلّا قَليلًا

Ali Unal

When you (O believers) set forth for (the campaign during which they think that you are sure) to take gains of war, those who stayed behind (aforetime) will say: “Let us go with you.” They desire to alter God’s decree. Say (to them): “You will by no means come with us. That (decision) regarding you is what God declared before.” Then they will say: “Rather, you are jealous of us.” But the fact is that they are lacking in discernment and understanding, except a very little.¹

After the Treaty of Hudaybiyah, the believers took several tribes under control, and conquered Khaybar. Once the hypocritical desert Arabs saw the Muslims conquering all their enemies, they wanted to participate in the Campaign of Khaybar with the hope of gaining spoils. However, God decreed that only those who had taken part in the Campaign of the Minor Pilgrimage could participate in this campaign. So they were left devoid of the war-gains that they had so craved.