וַיַּעֲבֹ֨ר יְהוָ֥ה ׀ עַל־פָּנָיו֮ וַיִּקְרָא֒ יְהוָ֣ה ׀ יְהוָ֔ה אֵ֥ל רַח֖וּם וְחַנּ֑וּן אֶ֥רֶךְ אַפַּ֖יִם וְרַב־חֶ֥סֶד וֶאֱמֶֽת ׀
And the LORD passed by before him, and proclaimed: ‘The LORD, the LORD, God, merciful and gracious, long-suffering, and abundant in goodness and truth;
Rashi on Exodus
ה׳ ה׳ THE LORD, THE LORD — This is the attribute of Divine mercy. The one (the first ה׳) alludes to God having mercy on the sinner before he sins and the other after he has sinned and repented (Rosh Hashanah 17b).
Ramban on Exodus
AND THE ETERNAL PASSED BY BEFORE HIM. This means that He fulfilled His promise to Moses, I will make all My goodness pass before thee.494Verse 19.