In פרשת קדושים, we have the Mitzva of ערלה. This is the commandment to wait three years before eating the fruit of the tree.
There is a statement that says that ערלה is הלכה למשה מסיני. It is a puzzling statement because ערלה is clearly mentioned in the Torah. What aspect is handed down from Hashem to Moshe Rabbeinu.
The הלכה למשה מסיני applies to חוץ לארץ. In Israel, the laws of ערלה applies everywhere and in all circumstances. When in doubt, we must take the strict ruling. However, in חוץ לארץ when there is a doubt, we can be lenient. ערלה is observed outside of Israel when it is definite. This is the הלכה למשה מסיני that we go לקולא in חוץ לארץ.