My son, do not let your past carelessness make you lose hope

Ibn-ul-Jawzee advised his son (the misguided one):
 "My son, do not let your past carelessness make you lose hope of achieving good, for many people have come back to wakefulness after long sleep."
'Laft al-Kabid ila Naseehah al-Walad'

“Have taqwa of Allah, and have a truthful tongue.

Imam Sufyan At Thawree said :
“Have taqwa of Allah, and have a truthful tongue. Have sincerity and do deeds of various nature without there being any deception or treachery therein. Indeed Allah sees you although you cannot see Him, and He is with you wherever you may be, and nothing of your affairs is hidden to Him. Do not be deceitful to Allah lest He returns that to you, for indeed, whoever attempts to deceive Allah, He will deceive him (i.e. make his plot turn back to him), and remove his faith from him whilst his soul does not feel it… Perfect your inner reality and Allah shall perfect your outer reality. Rectify what is between you and Allah, and Allah shall rectify what lies between you and the people.”

Regret over misdeeds erases them

"Regret over misdeeds erases them, and pride over good deeds ruins them" 

- Ali ibn Abi Talib

Forgiveness is more beloved to God than vengeance

Ibn Qayyim said, “Forgiveness is more beloved to God than vengeance; mercy is more beloved to Him than punishment; acceptance is more beloved to Him than wrath; and grace is more beloved to Him than justice.”

Whoever seeks to compete with you in your religion

The righteous salaf were as fearful of their good deeds being squandered, or not being accepted, as the present generation is certain that their neglect will be forgiven.
Al-Hasan Al-Basree

In our view, a person does not have an understanding of the religion until he thinks of a hardship as being a blessing, and a comfort and luxury as being a hardship.
Sufyaan Ath Thawree

Whoever seeks to compete with you in your religion, compete with him; whoever seeks to compete with you in this world, let him have it.
Al-Hasan Al-Basree

‎"There is nothing more harmful to the branches of Knowledge and its people than those who enter themselves into it and they are not from its people. They are ignorant and yet they think they have Knowledge, they cause corruption whilst thinking they are correcting the affairs."
This is a saying of Talq b. Habîb – Allâh have mercy on him. In Ibn Abî Al-Dunyâ, Al-Tawbah article 62.

‎"The right of Allah is too great and heavy for the creation to fulfill and the blessings of Allah are too many to enumerate, but you should remain repentant, morning and evening."
Talq b. Habîb – Allâh have mercy on him. In Ibn Abî Al-Dunyâ, Al-Tawbah article 62.

Tawbah part 3

We have now been going through two of the benefits of repentance. It wipes away our sins and it admits us to Paradise. The third benefit is that it renews our faith, our iman. You know, the Prophet, aleyhi salaato wasalaam, he said that our iman wears out just like clothes wears out, so we should renew our iman. And if we are sincere about our tawbah we will see and feel how our hearts will start to thaw, to become soft again. Our hearts will be alive again. When we reflect to ourselves about what we did, or didn’t do, we will begin to feel the wounds from that disobedience. It can be minor sins, or major sins, or a small sin that we are constantly doing. The sins we do are in level with our iman. If our iman is low, we don’t care much about what we do, we might even like the sins we do and don’t refrain or regret doing them. Or we do them openly. Our iman and our sins are in a direct relationship. Every time we commit a sin, our iman diminishes, it gets lower. When we leave the sins, leave the things that displeases Allaah subhano wata’ala, our iman will rise. There are many ayat, verses in the Koran about this and also ahadeeth. For example the Prophet, aleyhi salato wasalaam, said, "The one who commits illegal sexual intercourse is not a believer at the time of committing illegal sexual intercourse, and a thief is not a believer at the time of committing theft, and a drinker of alcoholic drink is not a believer at the time of drinking. Yet, (the gate of) repentance is open thereafter" (Al-Bukhari 8, 801). At the time we are doing these actions, our iman isn’t completely cancelled, but it in such a low level that we are able to commit these wrong actions, these sins. When our iman is high, we do not commit these mistakes or these sins. In an another hadeeth, the Prophet, aleyhi salato wasalaam, says: “When an adulturer commits adultery, the iman leaves him.”

Tawbah part 2

Tawbah to the believer is more important than air is to a human being. Imagine that. How can we live without air? It’s impossible, right. So how can we not do tawbah? We must strive to do tawbah regularly. And as being one of those who regularly repents, we can gain it’s benefits. Because you know, there are several benefits from doing tawbah.

The first one is that Allaah subhano wata’ala wipes away our sins! I already mentioned the hadeeth where the Prophet, aleyhi salaato wasalaam, says that the one who repents from sin is like the one without sin. It could be a specific sin or more in general, the way we lead our life before that was not according to islam.

Tawbah part 1

The word Tawbah litterally means ’to return’. For us muslims it means to leave that what Allaah, subhanu wa ta’ala, has forbidden and to return to Him and to what He has commanded. To return to Allaah, to make tawbah, is a very important part of our islam, our submission to Allaah. In soorah al-Baqarah it says:

إِنَّ ٱللَّهَ يُحِبُّ ٱلتَّوَّٲبِينَ
“Truly, Allâh loves those who turn unto Him in repentance” (2:222)

and this tawbah, is so important, because our destination in the hereafter is dependant on it, just as Allaah says in soorah An-Noor:

وَتُوبُوٓاْ إِلَى ٱللَّهِ جَمِيعًا أَيُّهَ ٱلۡمُؤۡمِنُونَ لَعَلَّكُمۡ تُفۡلِحُونَ
“And all of you beg Allâh to forgive you all, O believers, that you may be successful.” (24:31)