The definition of righteousness:

Taqwa is when a slave of Allah seeks to protect himself from the punishment of Allah by adhering to that which Allah has legislated and abstains from that which Allah has prohibited.

1. Having taqwa is a reason for one to be successful as Allah says in the Quran:

وَاتَّقُوا اللَّهَ لَعَلَّكُمْ تُفْلِحُونَ
“and fear Allah that you may be successful” 2:189

2. Having taqwa is from the reasons for one to increase in knowledge as Allah makes clear in the Quran:

وَاتَّقُوا اللَّهَ وَيُعَلِّمُكُمُ اللَّهُ وَاللَّهُ بِكُلِّ شَيْءٍ عَلِيمٌ
“So be afraid of Allah; and Allah teaches you. And Allah is the All-Knower of each and everything.” 2:282

3. Allah has prepared the gardens of paradise for those who have taqwa as He says:

وَسَارِعُوا إِلَىٰ مَغْفِرَةٍ مِّن رَّبِّكُمْ وَجَنَّةٍ عَرْضُهَا السَّمَاوَاتُ وَالْأَرْضُ أُعِدَّتْ لِلْمُتَّقِين
“And to forgiveness from your Lord and a garden [i.e., Paradise] as wide as the heavens and earth,  prepared for those who fear Allah.” 3:133

لَٰكِنِ الَّذِينَ اتَّقَوْا رَبَّهُمْ لَهُمْ جَنَّاتٌ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ خَالِدِينَ فِيهَا نُزُلًا مِّنْ عِندِ اللَّهِ

“But, for those who fear their Lord, are Gardens under which rivers flow (in Paradise); therein are they to dwell (for ever), an entertainment from Allah.” 3:198

4. By having taqwa one truly thanks Allah for that which Allah has bestowed upon him, as he says:
فَاتَّقُوا اللَّهَ لَعَلَّكُمْ تَشْكُرُون
“Then fear Allah so you may be from the grateful.” 3:123

5. It’s from the reasons Allah accepts a good deed as he says:

إِنَّمَا يَتَقَبَّلُ اللَّهُ مِنَ الْمُتَّقِين
“Indeed Allah only accepts from those who fear him.”5:27 взять деньги в долг на карту