You have given joy to my heart. The people of Israel say that the nations of the world who have observed the seven Noahide laws receive peace in this world and will be rewarded in the world to come. We, who have been commanded with 613 mitzvot, can only imagine the greater reward that awaits us in the next world. Therefore, when we see the peace of the nations of the world, we rejoice and say, "You have given joy to my heart."
Rabbi Yehoshua ben Levi gave a parable about a king who hosted a feast and seated his guests at the entrance of a kennel. The guests saw dogs coming out with muzzles, hooves, and the heads of calves. The guests wondered, "What kind of feast do these dogs have that they are treated better than us?" The nations of the world are compared to these dogs, as it says in Isaiah 56:11, "And the dogs are greedy."
If the nations of the world are at peace in this world, how much more so will Israel be at peace in the future world. Therefore, we say, "You have given joy to my heart."