﴿ فَلَمَّا دَخَلُوا۟ عَلَىٰ يُوسُفَ ءَاوَىٰٓ إِلَيْهِ أَبَوَيْهِ وَقَالَ ٱدْخُلُوا۟ مِصْرَ إِن شَآءَ ٱللَّهُ ءَامِنِينَ ﴾

“AND WHEN they [all arrived in Egypt and] presented themselves before Joseph, he drew his parents unto himself, saying, "Enter Egypt! If God so wills, you shall be secure [from all evil]!"”

Here the ‘couch’ does not mean a royal throne but the seat where Joseph used to sit and discharge the duties of his post; here prostration (sajdah) does not mean lying face down in the usual sense but bowing down and kneeling (ruku‘). This form of obeisance to a great man was prevalent in ancient times.