Once the Prophet Muhammad (PBUH) stepped forward to the mamber to speak to the Sahaba karams (R.A). He said amen when he step up at the first step of the mamaber, then he again said amen at the second step then again at the third step.
Sahaba karams (R.A) inquired about the event, that why prophet Muhammad (PBUH) do that.

He then adressed, that Hazrat Jibraeel had come to him, When he took first step, hazrat Jibraeel said, Whoever found his parents in the old age, and he not effort to get Heaven by serving them, curse upon that person. Then Prophet Muhammad Said Amen, At the next step Hazrat Jibraeel said, whoever listen the Prophet Muhammad(PBUH) name and doesnot send blessings to Muhammad(PBUH), curse upon that person, Hazrat Muhammad again said Amen, At the third step, hazrat Jibraeel said, whoever find Ramadan-ul-mubarak in his life, and lost the oppurtunity to get blessings and maghfirat from Allah, curse upon him, The Prophet Muhammad(PBUH) replied Amen ...........

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Kami kis shae ki hai tere khazaane me mere Allah
Jhukaa ke sar jo maangun teri rehmat mil hi jaaegi...