The Romans
وَمَآ ءَاتَيْتُم مِّن رِّبًا لِّيَرْبُوَا۟ فِىٓ أَمْوَٰلِ ٱلنَّاسِ فَلَا يَرْبُوا۟ عِندَ ٱللَّهِ ۖ وَمَآ ءَاتَيْتُم مِّن زَكَوٰةٍ تُرِيدُونَ وَجْهَ ٱللَّهِ فَأُو۟لَـٰٓئِكَ هُمُ ٱلْمُضْعِفُونَ
And whatever you give for interest to increase within the wealth of people will not increase with Allah. But what you give in zakah, desiring the countenance of Allah - those are the multipliers.
Nearby ayahs help place verse 30:39 in sequence and meaning.
أَوَلَمْ يَرَوْا۟ أَنَّ ٱللَّهَ يَبْسُطُ ٱلرِّزْقَ لِمَن يَشَآءُ وَيَقْدِرُ ۚ إِنَّ فِى ذَٰلِكَ لَـَٔايَـٰتٍ لِّقَوْمٍ يُؤْمِنُونَ
Do they not see that Allah extends provision for whom He wills and restricts [it]? Indeed, in that are signs for a people who believe.
فَـَٔاتِ ذَا ٱلْقُرْبَىٰ حَقَّهُۥ وَٱلْمِسْكِينَ وَٱبْنَ ٱلسَّبِيلِ ۚ ذَٰلِكَ خَيْرٌ لِّلَّذِينَ يُرِيدُونَ وَجْهَ ٱللَّهِ ۖ وَأُو۟لَـٰٓئِكَ هُمُ ٱلْمُفْلِحُونَ
So give the relative his right, as well as the needy and the traveler. That is best for those who desire the countenance of Allah, and it is they who will be the successful.
ٱللَّهُ ٱلَّذِى خَلَقَكُمْ ثُمَّ رَزَقَكُمْ ثُمَّ يُمِيتُكُمْ ثُمَّ يُحْيِيكُمْ ۖ هَلْ مِن شُرَكَآئِكُم مَّن يَفْعَلُ مِن ذَٰلِكُم مِّن شَىْءٍ ۚ سُبْحَـٰنَهُۥ وَتَعَـٰلَىٰ عَمَّا يُشْرِكُونَ
Allah is the one who created you, then provided for you, then will cause you to die, and then will give you life. Are there any of your "partners" who does anything of that? Exalted is He and high above what they associate with Him.
ظَهَرَ ٱلْفَسَادُ فِى ٱلْبَرِّ وَٱلْبَحْرِ بِمَا كَسَبَتْ أَيْدِى ٱلنَّاسِ لِيُذِيقَهُم بَعْضَ ٱلَّذِى عَمِلُوا۟ لَعَلَّهُمْ يَرْجِعُونَ
Corruption has appeared throughout the land and sea by [reason of] what the hands of people have earned so He may let them taste part of [the consequence of] what they have done that perhaps they will return [to righteousness].