It is only obligatory upon the Messenger to convey the Message

Concerning Allah's statement,

﴿إِلاَّ بَلاَغاً مِّنَ اللَّهِ وَرِسَـلَـتِهِ﴾

((Mine is) but conveyance from Allah and His Messages,) This is an exception related to the previous statement,

﴿لَن يُجِيرَنِى مِنَ اللَّهِ أَحَدٌ﴾

(None can protect me from Allah's punishment,) meaning, `nothing can save me from Him and rescue me except my conveyance of the Message that He has obligated me to carry out.' This is as Allah says,

﴿يَـأَيُّهَا الرَّسُولُ بَلِّغْ مَآ أُنزِلَ إِلَيْكَ مِن رَّبِّكَ وَإِن لَّمْ تَفْعَلْ فَمَا بَلَّغْتَ رِسَالَتَهُ وَاللَّهُ يَعْصِمُكَ مِنَ النَّاسِ﴾

(O Messenger! Proclaim which has been sent down to you from your Lord. And if you do not, then you have not conveyed His Message. Allah will protect you from mankind.) (5:67) Then Allah says,

﴿وَمَن يَعْصِ اللَّهَ وَرَسُولَهُ فَإِنَّ لَهُ نَارَ جَهَنَّمَ خَـلِدِينَ فِيهَآ أَبَداً﴾

(and whosoever disobeys Allah and His Messenger, then verily, for him is the fire of Hell, he shall dwell therein forever.) meaning, `I will convey unto you all the Messages of Allah, so whoever disobeys after that, then his reward will be the fire of Hell wherein he will abide forever.' This means, they will not be able to avoid it nor escape from it. Then Allah says,

﴿حَتَّى إِذَا رَأَوْاْ مَا يُوعَدُونَ فَسَيَعْلَمُونَ مَنْ أَضْعَفُ نَاصِراً وَأَقَلُّ عَدَداً ﴾

(Till, when they see that which they are promised, then they will know who it is that is weaker concerning helpers and less important concerning numbers.) meaning, until these idolators from the Jinns and humans see what has been promised to them on the Day of Judgement. Then on that day, they will know who's helpers are weaker and fewer in number -- them or the believers who worship Allah alone. This means that the idolators have no helper at all and they are fewer in number than the soldiers of Allah.

﴿قُلْ إِنْ أَدْرِى أَقَرِيبٌ مَّا تُوعَدُونَ أَمْ يَجْعَلُ لَهُ رَبِّى أَمَداً - عَـلِمُ الْغَيْبِ فَلاَ يُظْهِرُ عَلَى غَيْبِهِ أَحَداً - إِلاَّ مَنِ ارْتَضَى مِن رَّسُولٍ فَإِنَّهُ يَسْلُكُ مِن بَيْنِ يَدَيْهِ وَمِنْ خَلْفِهِ رَصَداً - لِّيَعْلَمَ أَن قَدْ أَبْلَغُواْ رِسَـلَـتِ رَبِّهِمْ وَأَحَاطَ بِمَا لَدَيْهِمْ وَأَحْصَى كُلَّ شَىْءٍ عَدَداً ﴾

(25. Say: "I know not whether that which you are promised is near or whether my Lord will appoint for it a distant term.'') (26. "The All-Knower of the Unseen, and He reveals to none His Unseen.'') (27. Except to a Messenger whom He has chosen, and then He makes a band of watching guards to march before him and behind him.) (28. Till he knows that they have conveyed the Messages of their Lord. And He surrounds all that which is with them, and He keeps count of all things.)