Q 15:51

And tell them about the guests (i. e., the angels) of Ibrahim (51)When they entered upon him, and said: "Salaman (peace!)." He said: "Indeed we are frightened of you. (52)They said: "Do not be afraid! We bring you the good news of a boy possessing much knowledge and wisdom. (53)He said: "Do you give me this good news while old age has overtaken me? Of what then is your news about? (54)They said: "We give you good news in truth. So do not be of those who despair. (55)He said: "And who despairs of the mercy of his Lord except those who are astray? (56) The Guests of Ibrahim and their Good News of a Son for Him Allah is saying: 'Tell them, O Muhammad, about the story of ضَيْفِ إِبْرَاهِيمَ (the guests of Ibrahim.)' دَخَلُوا عَلَيْهِ فَقَالُوا سَلَامًا قَالَ إِنَّا مِنكُمْ وَجِلُونَ (they entered upon him, and said: "Salaman (peace!)." He said: "Indeed we are frightened of you.") meaning that they were scared. The reason for their fear has been mentioned previously, which is that they noticed that these guests did not eat of the food that was offered, which was a fattened calf. قَالُوا لَا تَوْجَلْ (They said: "Do not be afraid!...") meaning, do not be scared. وَبَشَّرُوهُ بِغُلَامٍ عَلِيمٍ (We bring you the good news of a boy possessing much knowledge and wisdom.) this refers to Ishaq, as was previously mentioned in Surat Hud. Then قَالَ (He said) meaning he spoke with wonder and astonishment, asking for confirmation, because he was old and his wife was old: أَبَشَّرْتُمُونِي عَلَىٰ أَن مَّسَّنِيَ الْكِبَرُ فَبِمَ تُبَشِّرُونَ (Do you give me this good news while old age has overtaken me? Of what then is your news about?) They responded by confirming the good news they had brought, good news after good news: قَالُوا بَشَّرْنَاكَ بِالْحَقِّ فَلَا تَكُن مِّنَ الْقَانِطِينَ (They said: "We give you good news in truth. So do not be of those who despair.")