Exodus 6:3

And I appeared unto Abraham, unto Isaac, and unto Jacob, by the name of God Almighty, but by my name JEHOVAH was I not known to them.

And I appeared unto Abraham, unto Isaac, and unto Jacob, by the name of God Almighty,.... Able to fulfil all his purposes, promises, and covenant, with whom nothing is impossible; or Elshaddai, God all-sufficient, who has a sufficiency of happiness in himself, and everything to supply the wants of his creatures in things temporal and spiritual, see Genesis 17:1:

but by my name JEHOVAH was I not known to them; which he had in the preceding verse called himself by. This is not to be understood absolutely; for it is certain that he had made himself known by this name, and this name was known unto Abraham, Isaac, and Jacob,

Genesis 15:6, and but comparatively, as some think; that is, he was not so much made known to them by the one name as the other; though it may be questioned whether the one was more used in speaking to them than the other; wherefore others think, as Saadiah Gaon, that the word only is to be supplied, as in Genesis 32:28 and the sense to be, that by his name Jehovah he was not only made known to them, but by his name Elshaddai, and others also; and others reconcile the difficulty thus, that though the name Jehovah itself was known to the patriarchs, by which they were assured that God is eternal, immutable, and faithful to his promises; yet he was not known as to the efficacy of this name, or with respect to the actual performance of his promise, as he now would be by delivering the children of Israel out of Egypt, and bringing them into the land of Canaan; though perhaps, by reading the words with an interrogation, the clause will appear more plain, "and by my name Jehovah was I not known to them?" {t} verily I was. Josephus {u} says, this name was not before made known to men, and that it was not lawful for a man to speak it; and this is the common notion of the Jews, that it is ineffable, and not lawful to be pronounced, and therefore they put Adonai and Elohim in the room of it, and the vowel points of these words to it, which is a false and superstitious notion: this name was known among the Heathens; it is the same with iaw in the oracle of Apollo {w}; and Diodorus Siculus {x} says, that with the Jews Moses is said to give laws from a God called "IAO", and is the same which in Philo Byblius {y} is called Jevo; and both are no other than a corruption of Jah or Jehovah; and perhaps the tetraktuv of the Pythagoreans {z}, by which they swore, is the same with the tetragrammaton, or this word of four letters, with the Jews.

{t} Vid. Noldium, No. 788.
{u} Antiqu. l. 2. c. 12. sect. 4.
{w} Cornelius Labeo de oraculo Apoll. Clarii apud Macrob. Saturnal. l. 1. c. 18.
{x} Bibliothoc. l. 1. p. 84.
{y} Apud Euseb. Praepar. Evangel. l. 1. c. 9. p. 31.
{z} Carmin. Aurea Pythagor. l. 47. & Hierocles in ib. p. 225, 277. Porphyr. de Vita Pythagor. p. 189.