The reason why you should invest in your marriage is because firstly it can affect your akhira in an enormous way and as a husband you have a lot of responsibility on your shoulders both for your wife and family. Secondly it affects your home life, if you have a bad marriage then it will likely be a source of sadness and anxiety. Thirdly it can affect your health and wellbeing. Fourthly it can affect your career and finances. Fifth this has a chance of affecting your children’s upbringing and your direct and extended family relationships. Finally, the ummah is made of individual family units, if family units are dysfunctional it will affect the ummah as a whole.
You should invest in your marriage: through time, money and energy as this is an investment in yourself first and foremost and then your family.
You can invest in your marriage through spending time and money on your family and serving them, you can invest it in yourself through increasing your understanding of maintaining relationships and developing yourself so that you can lead your family in a better way.
You can invest in your family through learning and advice from others but not allowing them to interfere or unduly influencing you.
