Quran 9:46

وَلَوۡ أَرَادُواْ ٱلۡخُرُوجَ لَأَعَدُّواْ لَهُ ۥ عُدَّةً۬ وَلَـٰكِن ڪَرِهَ ٱللَّهُ ٱنۢبِعَاثَهُمۡ فَثَبَّطَهُمۡ وَقِيلَ ٱقۡعُدُواْ مَعَ ٱلۡقَـٰعِدِينَ ٤٦

Had they really wanted to mobilize, they would have prepared for it thoroughly. But ALLAH disliked their participation, so He discouraged them; they were told, "Stay behind with those who are staying behind."