FWP:
Hali provides the obvious pious reading; Asi, as quoted by Baqir, lays out the worldly-love one. Naturally, both are possible. The first line sets up the ambiguity-- the pious suggestion of looking up at the heavens, from whence descend disasters [balaa))e;N], and then of reflecting on the power of God. The second line is such a truism when applied to God-- namely, that when God gets angry he can do powerful (bad) things-- that it's hard to avoid moving beyond it, to the alternative reading in which the thought is of the human beloved.
The really striking thing is the omission of bhii from the second line. If that word were there then we could read, in anger she too has commanding power; thus her power would be seen in the light of God's celestial power, and as an echo of it. But Ghalib's refusal to put in the bhii means that only one powerful ruler is thought of in both lines: if the verse is about God, then it is a cliched commonplace; if it's about the beloved, then she entirely displaces God from the lover's horizon. When the speaker looks at the heavens, the proper domain of God alone, he doesn't think of God at all, it's she whom he thinks of-- for she has masterful power when she's angry. God, in short, is nowhere, since not even looking at the heavens serves to evoke him, and the very quality he is famous for-- being powerful and dangerous when angered-- is blithely transferred to the beloved. Her status as an idol has rarely been so unselfconsciously confirmed.
For another meditation on the sky, the beloved, and memory, see {136,1}. There are also intriguing similarities with {200,3}.
Mir plays his own tricks with this kind of ambiguity in M{139,6}.
Hali:
That is to say, when I have looked at the sky, the Lord comes to mind, because the oppression that falls from the sky is due to His command.
==Urdu text: Yadgar-e Ghalib, p. 141