Antiquated uses of haber

Question

Today, someone told me that haber can be used to indicate possession, apparently because in early Spanish haber was used to mean tener. They gave the specific example of:

Hemos un bocadillo (We have a sandwich)

Is this a valid construct? I was told that although 90% of haber's uses are as an auxiliary verb, its function as a verb to indicate a possessive is not entirely gone, and that erudite individuals can use haber in this way to sound intelligent or archaic, in a similar way to how contemporary English speakers use thou.

Also - In Spanish, the phrase 'haber de' can be used to indicate an obligation in a way that is similar to the construct 'tener que'. For example:

He de trabajar mañana (I have to work tomorrow)

The same individual also told that this is rare, archaic way of forming the future tense and that the endings for future tense verbs come from the endings of haber's present tense conjugations.

He de ir a la playa.
Iré a la playa.

Are these two statements above really equivalent? Were they at any point in time?

Answer 1

Using haber to express possession could certainly be used back in the day (where it had the imperative forms habe and habed), but it developed today into the virtually exclusively auxiliary (for perfects) and impersonal (for existential statements) verb we have today. There are a few situations where you might use it in legal or other contexts where language has been stuck in formulaic constructions (such as habida cuenta de - teniendo en cuenta el hecho de), but that's really about it.

haber de [inf.] can be used to indicate obligation. It's considered equivalent to tener que as you mention, just that tener que is more common.

Haber de [inf.] for future is still seen in modern Spanish, though certainly no where near as common as simple future or the other periphrastic future of ir a [inf.]. This usage is no where near as common as haber de for obligation, but you can absolutely use it as a way to indicate the future.¹

Haber is actually where the future tense came from in Spanish, a combination of an infinitive and the verb haber. So you'd have nadar he or comer has which eventually were reduced to nadaré and comerás (for a time, you could even find the pronouns in between, as in dar me has -> darmeás -> me darás_/darasme.

Note that there are other older uses that you'll see once in a while. One of them is for denoting time, instead of using hacer. So instead of hace cinco años que..., you can say cinco años ha que.... There's also the construction haberselas that allows the archaic conjugation of habermos: Nos las habemos con esa gentuza.

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^{1. However, they are not exactly equivalent. Not that iré is true future, whereas he de ir, in its future interpretation, is still technically present tense. In simple statements, this makes no difference, but can affect tense ordering in subordinate clauses.}

Answer 2

in early Spanish "haber" was used to mean "tener"

That's right, and the evolution can be followed from the English analog:

Yo he un caballo = I have a horse (old Spanish)

Yo he un caballo comprado = I have a bought horse (here 'comprado/bought' is an adjetive)

Yo he comprado un caballo = I have bought a horse (this was originally the same as above, but "comprado" evolved from adjective to verb, in participle)

The only difference is that in English "have" retained the old meaning, as a plain verb (to posess) and it also gained the new meaning (auxiliary verb). While in Spanish the old use almost disappeared.

This is explained (in Spanish) here.

Today the old meaning ("haber" = "tener") is rare.

See also the dictionary

Also - In Spanish, the phrase 'haber de' can be used to indicate an obligation in a way that is similar to the construct 'tener que'.

Yes, that's also right. It's a rather convoluted way of express some obligation, or purpose, or expectation - or simply: future.

He de trabajar mañana (I have to work tomorrow)

Not extremely rare, but kind of special. Some examples:

Has de saber que... (You should/must know/learn that...)

No he de descansar hasta haber entendido... (I won't rest until having understood...)

Es la realidad, y hemos de aceptarla (That's reality, and we must accept it)

Regarding

He de ir a la playa.

Iré a la playa.

Are these two statements above really equivalent? Were they at any point in time?

At least in current usage, the second is the normal one, the first is a "stylized" way of saying the same, it could be used to emphasize obligation, or determination.