Shaykh Fawzaan (hafidhahullah) said,
"The objective of the statement of La ilaha illAllah is not saying it with the tongue only without understanding it; it is essential that you learn the meaning of La ilaha illAllah; as for you saying it without knowing its meaning, then you do not affirm what it proves and how can you affirm a thing you are ignorant of? Thus, it is essential that you know its meaning until you affirm it and you affirm with your heart what your tongue articulates of it; so it is binding that you learn the meaning of La illah illAllah, as for mere articulation of the tongue without understanding its meaning, then this will not benefit at all"
Explanation of the Treatise "The Meaning of the Statement of Tawheed" by Shaykh Muhammad Ibn Abdul Wahhab - Explained by Shaykh Saalih Al-Fawzaan (hafidhahullah) pg. 10