I want my children to be firm on their deen, so I am strict and I raise my voice. Isn’t harshness sometimes necessary to keep them on the straight path?
The worry behind your question is real, and it deserves a real answer rather than reassurance. So let us look at what actually holds a child on the path, and whether a raised voice is that thing.
When Allah described how His Messenger (peace be upon him) gathered a hard people around him and held them there, He did not name sternness. He named gentleness, and then warned about its opposite.
“So by the mercy of Allah you were lenient with them. And had you been harsh and hard of heart, they would have dispersed from around you.”
Qur’an, Aal-e-Imran 3:159 · meaning
Notice what that verse settles. The message was the truest there has ever been and the man carrying it was the most perfect, and still it is said that harshness would have scattered them. If grown men could not carry it, a child’s heart certainly cannot. Deen is not pushed into a child, it is made lovable to him. A raised voice can bend the small body standing in front of you, but it quietly teaches the heart to shut its door when you come near, and a closed heart does not carry deen into adulthood.
And mercy in the home is not an extra. The Prophet (peace be upon him) tied the mercy we receive to the mercy we give.
“Whoever is not merciful will not be shown mercy.”
The Prophet (peace be upon him), Sahih al-Bukhari (5997) · meaning
Gentleness is not weakness, and it is not the loosening of your standards. It is a quality Allah Himself loves, which is why firmness and gentleness can walk together: the expectation clear and unmoving, the manner soft.
“Indeed Allah is gentle and loves gentleness in all matters.”
The Prophet (peace be upon him), Sahih al-Bukhari (6927) · meaning
Those who have studied how faith passes from one generation to the next found what watchful people already knew. A parent’s warmth, and a father’s warmth most of all, is the thread along which deen travels to a child, while what is pressed in mainly by force tends to be set down once the child is grown and free. So keep your firmness, but let it show as calm consistency rather than volume. Raise the expectation, not the voice. That is not doing less for their deen, it is doing the most that can be done.
One small step: The next time you feel your voice about to rise at your child, pause, lower it by half, and say the same correction gently while placing a hand on their shoulder.