Umayr bin Said al Ansari was only 17 years old when Allah sent an Aya because of him.
His mother became widow when Umayr was still young and they were poor. She had to marry another man, who was Julas ibn Suwayd al-Awsi.
He was wealthy and after marriage he became very generous and kind step-father for Umayr and husband for his mother.
Umayr became Muslim at early age, and was known as a frequent visitor to Masjidal Nabawi.
Our history is about the days preceding the Tabuk Campaign, when Muslims in groups to enroll for the Campaign. But due to lack of resources they had to be rejected.
Coming from Masjid, Umayr reflected this to his Step-Father, and that is when he was shocked by the reply he heard:
"If Muhammad is a real Prophet as he claims, we are all worse than donkeys"
Hearing this, Umayr was caught in between his duty towards Islam, and love and appreciation to his Step-Father. But his love to Allah and Muhammad, peace be upon Him, took over and he reported the case to RasulUllah, peace be upon Him.
Having been questioned Julas started denying what he had said and accused Umayr of lying.
Sahabas were turning towards Umayr with disbelief in his words, and calmly condemned young man.
All Umayr could do was to ask Allah, who hears and responds to his slave's supplications.
And that is when Muhammad, peace be upon Him, pronounced the following ayat:
يَحْلِفُونَ بِاللَّـهِ مَا قَالُوا وَلَقَدْ قَالُوا كَلِمَةَ الْكُفْرِ وَكَفَرُوا بَعْدَ إِسْلَامِهِمْ وَهَمُّوا بِمَا لَمْ يَنَالُوا ۚ وَمَا نَقَمُوا إِلَّا أَنْ أَغْنَاهُمُ اللَّـهُ وَرَسُولُهُ مِن فَضْلِهِ ۚ فَإِن يَتُوبُوا يَكُ خَيْرًا لَّهُمْ ۖ وَإِن يَتَوَلَّوْا يُعَذِّبْهُمُ اللَّـهُ عَذَابًا أَلِيمًا فِي الدُّنْيَا وَالْآخِرَةِ ۚوَمَا لَهُمْ فِي الْأَرْضِ مِن وَلِيٍّ وَلَا نَصِيرٍ (9:74)
They swear by Allah that they did not say [anything against the Prophet] while they had said the word of disbelief and disbelieved after their [pretense of] Islam and planned that which they were not to attain. And they were not resentful except [for the fact] that Allah and His Messenger had enriched them of His bounty. So if they repent, it is better for them; but if they turn away, Allah will punish them with a painful punishment in this world and the Hereafter. And there will not be for them on earth any protector or helper.(9:74)
Julas made tawba and ever since whenever Umayr was mentioned by Julas he was saying:
"May Allah give Jannat to Umayr, he prevented me from falling into Nifaq"
* - Nifaq - Hypocrisy