Allah said that Ibrahim and Isma`il supplicated to Him,

﴿رَبَّنَا وَاجْعَلْنَا مُسْلِمَيْنِ لَكَ وَمِن ذُرِّيَّتِنَآ أُمَّةً مُّسْلِمَةً لَّكَ وَأَرِنَا مَنَاسِكَنَا وَتُبْ عَلَيْنَآ إِنَّكَ أَنتَ التَّوَّابُ الرَّحِيمُ ﴾

(Our Lord! And make us submissive unto You and of our offspring a nation submissive unto You, and show us our Manasik, and accept our repentance. Truly, You are the One Who accepts repentance, the Most Merciful.)

Ibn Jarir said, "They meant by their supplication, `Make us submit to Your command and obedience and not associate anyone with You in obedience or worship.''Also, `Ikrimah commented on the Ayah,

﴿رَبَّنَا وَاجْعَلْنَا مُسْلِمَيْنِ لَكَ﴾

(Our Lord! And make us submissive unto You)

"Allah said, `I shall do that.'''

﴿وَمِن ذُرِّيَّتِنَآ أُمَّةً مُّسْلِمَةً لَّكَ﴾

(And of our offspring a nation submissive unto You)

Allah said, `I shall do that.'"

This supplication by Ibrahim and Isma`il is similar to what Allah informed us of about His believing servants,

﴿وَالَّذِينَ يَقُولُونَ رَبَّنَا هَبْ لَنَا مِنْ أَزْوَجِنَا وَذُرِّيَّـتِنَا قُرَّةَ أَعْيُنٍ وَاجْعَلْنَا لِلْمُتَّقِينَ إِمَاماً ﴾

(And those who say: `Our Lord! Bestow on us from our wives and our offspring the comfort of our eyes, and make us leaders of the Muttaqin) (25:74).

This type of supplication is allowed, because loving to have offspring who worship Allah alone without partners is a sign of complete love of Allah. This is why when Allah said to Ibrahim,

﴿إِنِّى جَـعِلُكَ لِلنَّاسِ إِمَامًا﴾

(Verily, I am going to make you an Imam (a leader) for mankind (to follow you)) Ibrahim said,

﴿وَمِن ذُرِّيَّتِى قَالَ لاَ يَنَالُ عَهْدِي الظَّـلِمِينَ﴾

("And of my offspring (to make leaders).'' (Allah) said, "My covenant (prophethood) includes not the Zalimin (polytheists and wrongdoers)'') which is explained by,

﴿وَاجْنُبْنِى وَبَنِىَّ أَن نَّعْبُدَ الاٌّصْنَامَ﴾

(And keep me and my sons away from worshipping idols)

Muslim narrated in his Sahih that Abu Hurayrah said that the Messenger of Allah said,

«إِذَا مَاتَ ابْنُ آدَمَ انْقَطَعَ عَمَلُهُ إِلَّا مِنْ ثَلَاثٍ: صَدَقَةٍ جَارِيَةٍ أَوْ عِلْمٍ يُنْتَفَعُ بِهِ أَوْ وَلَدٍ صَالِحٍ يَدْعُو لَه»

(When the son of Adam dies, his deeds end except for three deeds: an ongoing charity, a knowledge that is being benefited from and a righteous son who supplicates (to Allah) for him.)