Reference: http://www.alfawzan.af.org.sa/node/15428
Question: When children are upon goodness, is this a blessing [from Allaah]; and when they are corrupt, are they a curse?
Response: Without a doubt, indeed children are a blessing from Allaah if they are upon goodness; however, there is a reason for their being upon goodness, and that is good nurturing – the nurturing of the father towards them, as he ﷺ said:
[So] goodness does not come by accident, there has to be a reason – and that [reason] is good nurturing; because bad nurturing causes the children to deviate away from the sound natural disposition [towards worshiping Allaah alone – as they were created], as the Prophet ﷺ said:
And the nurturing of the father towards the children plays a big role – both in them being upon goodness, as well as their corruption; and he is responsible for them in front of Allaah Subhaanahu wa Ta’aala.