This excerpt is taken from Sheikh Hussain bin Mubarak Al-Mosuli's Arabic book Al-Awamer wal-Nawahi, whose Urdu translation has been done by Muhammad Sarwar Gohar Sahib under the title Ahkamat o Mamnoaat.
Prohibition of Losing Hope in Paradise
① Sayyiduna Abu Huraira (RA) narrates that the Messenger of Allah (PBUH) said:
لو يعلم المؤمن ما عند الله من العقوبة ما طمع فى الجنة، ولو يعلم الكافر ما عند الله من الرحمة ما قنط من الجنة
"If a believer comes to know about the punishment and torment with Allah, he should never hope for Paradise, and if a disbeliever comes to know about the mercy with Allah, he should never despair of Paradise."
Reference: Muslim, Kitab al-Tawbah 2755/23, Tirmidhi, Kitab al-Da'wat 3542. Musnad Ahmad, Baqi Musnad al-Mukathirin 2/446, Hadith 8436.
Prohibition of Saying 'If' and 'But'
① Sayyiduna Abu Hurairah رضي الله عنه reports that the Messenger of Allah صلی اللہ علیہ وسلم said:
"A strong believer is better and more beloved to Allah than a weak believer, and there is good in everyone. Desire that which benefits you, seek help from Allah, and do not be helpless. And if something befalls you, do not say: If I had done such and such, it would have been such and such, but say: What Allah has decreed and willed has happened, for 'if and but' opens the way for the work of Satan."
Reference: Sahih Muslim.